Poster abstracts

 

Planetary formation and evolution

 

Tracing the late formation and early evolution of young Sub-Neptune progenitors
Saugata Barat (University of Amsterdam)

Sub-Neptunes and super-Earths correspond to the most common population exoplanets, yet there are several burning questions regarding their formation and their early evolution. In this context the 23 Myr old V1298 Tau system, composed of three Neptunes/Sub-Neptunes transiting exoplanets, represents a unique opportunity to probe the early conditions of what are most likely super-Earth progenitors. We present observational campaigns dedicated to probe the atmospheres of the V1298 Tau planets to trace fossil records of their formation, though the determination of their mass, their elemental abundances and metallicity, and ongoing evolution though their atmospheric dynamics and escape. We find that the planets in this system have lower masses and much lower metal abundances than initially thought, and that atmospheric escape is occurring at lower rates than expected. Our puzzling findings challenges planet formation paradigms for small planets and we discuss our results in the context of planet formation, comparative exoplanetology with other young and mature systems, as well as within the same system.

 

Dynamic Disk Temperature and its Effect on Pebbles and Planet Formation
Areli Castrejon (University of Groningen, Kapteyn Astronomical Institute)

To date, thousands of exoplanets have been discovered; a sizeable amount of these planets lie in the intermediate mass range (1-10 Earth masses). The predominant theory to grow these planets is the pebble accretion paradigm. In this formulation, larger particles denoted as pebbles, feel drag from the gaseous disk and are accreted onto growing protoplanets. The efficiency of pebble accretion allows planetary embryos to grow quickly, before the disk dissipates. The evolution of the pebble surface density is highly dependent on the temperature structure chosen. We follow an evolving temperature structure with and without a dust sublimation front. We find that the temperature evolution cannot be ignored in calculating the pebble dynamics and this has implications for the growth of planets. A dynamic temperature leads to a longer-lived pebble surface density. The sustained surface density results in a large population of intermediate mass planets, in-line with observations.

 

Planet across space and time (PAST) III. Morphology of the Planetary Radius Valley as a Function of Stellar Age and Metallicity
Di-Chang Chen (Nanjing University), Di-Chang Chen, Jia-Yi Yang, Ji-Wei Xie, Ji-Lin Zhou, Subo Dong

Over 5,000 exoplanets have been identified and thousands of candidates are to be confirmed. What are the differences between planetary systems in different Galactic environments, and how do they evolve with time? To address these questions, we conduct a research project, dubbed Planets Across Space and Time (PAST). Here we present some first results of PAST series. We revisit the kinematic method for classification of Galactic components and extend the applicable range from ~ 100 pc to ~ 1, 500 pc from the sun in order to cover most known planet hosts. Furthermore, we revisit the Age-Velocity dispersion Relation (AVR), which allows us to derive kinematic age with a typical uncertainty of 10-20% for an ensemble of stars. Applying the above revised methods, we present catalogs of kinematic properties as well as other basic stellar parameters for 2174 host stars of 2872 planets and 35,835 Kepler stars. Using the above kinematic catalogs, we perform a systematical investigation into the planetary radius valley morphology in the Galactic context, i.e., thin/thick galactic disks, stellar age and metallicity abundance ([Fe/H] and [alpha/Fe]).

 

Did planet formation occur only recently? Evidences from kinematics and chemical properties of exoplanet host stars from GAIA DR3
Swastik Chowbay (Indian Institute of Astrophysics), Swastik Chowbay, Ravinder K Banyal et al

In this study, we examine the kinematic and chemical features of the largest number of 2627 exoplanets harbouring stars whose parameters have been uniformly determined. We combine photometric, astrometric, and spectroscopic data from the most recent Gaia DR3 to examine the various populations of exoplanets harbouring stars. Using spectroscopic data, we determined that stars hosting massive planets are metal-rich and $\alpha$-poor in comparison to stars hosting small planets. Kinematic analysis reveals that the host stars of small planets and giant planets differ in all aspects of galactic space velocity and orbital parameters. In addition, we find that small planet hosting stars have a marginally higher eccentricity and $Z_{max}$ (an indication of an older population) than their larger counterparts. Our spectroscopic and kinematic studies suggest that the small and giant planetary systems likely belong to population of stars with different ages, giants being younger than the small ones. Using the PARSEC isochrone grids and isochrone fitting methods, we also estimated the ages of stars bearing exoplanets. All together, three analyses show that gas giants may have stared forming after the interstellar medium was enriched by Type Ia supernovae, which occurred late in the history of Milky Way. At the same time, a large spread seen in various age indicators of small planet hosting stars implies that they formed throughout the GCE. Despite the fact that several previous studies hinted at similar conclusions, they were not robust because to smaller sample sizes and/or inhomogeneous stellar parameter estimations. Due to the fact that our investigation was conducted on the largest sample of stars that host exoplanets, our results are currently the most credible.

 

On the formation history of nearby Sun-like stars (and their planetary systems)
Philippe Gondoin (ESA exoplanet team)

Nearby Sun-like stars are prime targets for the detection and characterization of exo-planets and possibly exo-Earths. Understanding their formation history and determining the age of these stars (and their planetary systems) is thus essential.The present study addresses the formation history of nearby solar-type stars using the emission reversal in the cores of their Ca II H&K Fraunhofer lines as an age indicator. A representative sample of nearby (< 65pc) main-sequence G-type stars with near-solar metallicity and known magnetic activity levels is built from a catalogue of chromospheric activity indices (Gomes da Silva et al. 2021) derived from high-resolution spectra obtained with the HARPS spectrograph between 2003 and 2019, as compiled in the AMBRE project. I used an empirical age-activity relationship derived from stellar rotation period measurements in intermediate-age open clusters (Gondoin 2020) to infer the age distribution of these sample stars.

 

A unique testbed for the formation and evolution of small exoplanets: TOI-270
Maximilian Guenther (European Space Agency (ESA)), Laurel Kaye, Thomas Mikal-Evans, ASTEP, NGTS, SPECULOOS, TESS and TFOP science teams

The nearby exoplanet system TOI-270 provides an unparalleled opportunity to observationally probe hypotheses for planet formation and evolution. The system hosts one super-Earth and two sub-Neptunes near mean-motion resonances and transiting a bright (K-mag 8.25) M3V dwarf. Strangely, M-dwarf systems harbouring only super-Earths or only sub-Neptunes are ubiquitous. However, for still unknown reasons, systems with multiple planets spanning the radius valley are rare - and we know merely a handful of systems bright enough for precise mass measurements and atmospheric studies. To this end, TOI-270's planets are exceptionally favourable for detailed transit timing variation (TTV) and transmission spectroscopy observations. First, with the planets orbiting near low-order resonances (5:3 and 2:1), our extensive observing campaign with eight different observatories since 2018 yields clear TTV signals for planets c and d, with amplitudes of around 10 min and a super-period of circa 3 yr. Using dynamical models, we can thus significantly constrain their radii, mass ratios, and eccentricities. This adds to complementary radial velocity (RV) mass measurements from HARPS and ESPRESSO. Second, via HST and JWST transmission spectroscopy we can characterise and compare the atmospheres of two sub-Neptunes formed from the same protoplanetary nebula and test hypotheses like photoevaporation, core-powered mass-loss, and gas-poor formation. As one of the best-constrained small planet systems, TOI-270 can thus serve as a unique observational testbed for formation and evolution theories.

 

Studying exoplanet orbits & dynamics with allesfitter
Maximilian Guenther (European Space Agency (ESA)), Tansu Daylan

The orbits and dynamics of exoplanet systems can unveil their tales of formation, migration, star-planet interactions, and atmospheric properties. TESS, CHEOPS, and soon PLATO deliver an unprecedented wealth of new photometric data on this matter, while ground-based follow-up and radial velocity instruments add valuable insights. Here, I will present how we can unite and untangle all this data on exoplanets' orbits and dynamics using allesfitter. This open-source python software enables flexible and robust inference of stars and exoplanets from photometric and radial velocity data. Allesfitter offers a rich selection of orbital and transit/eclipse models, accommodating multiple exoplanets, multi-star systems, transit-timing variations, and phase curves. It can also help mitigate and/or study stellar variability, star spots, and stellar flares. I will highlight some of allesfitter's science output on examples of exoplanet dynamics (e.g., TOI-270 and TOI-216) and orbital phase curves (e.g., WASP-18 and WASP-121). With TESS' extended mission, CHEOPS in full swing, and PLATO on the horizon, a wealth of new data face us, allowing TTV and phase curve studies of dozens of such systems over many years.

 

Young planets are key: HIP 67522 b and TOI-4562 b
Alexis Heitzmann (Queen Mary University of London) et al.

 

A search of accreting protoplanets through high-angular resolution H alpha observations
Nuria Huélamo (CAB (CSIC-INTA))

Protoplanets embedded in disks are expected to accrete material from their surrounding media. As a result of this process, they can emit in accretion tracers like the H alpha line. In this work, we show the result from SPHERE/ZIMPOL observations to detect accreting protoplanets around five stars with (pre-)transitional disks. They were obtained in the H_alpha line and the adjacent continuum, combining spectral and angular differential imaging techniques to increase the contrast in the innermost regions close to the star. We do not detect any point-like source around any of the stars. When we compare our detection limits with different planetary models, we estimate an average upper limit to the accretion luminosity of < 10^-4 Lsun at 200 mas, which is 2 orders of magnitude higher that that previously estimated from the extrapolation of the L_Halpha - L_acc stellar relationship. We explain the lack of protoplanet detections as a combination of different factors, like e.g. episodic accretion, extinction from the circumstellar and circumplanetary disks, and/or a majority of low-mass, low-accreting planets. The JWST will help to shed light on the accretion process of planets at the earliest stages of their formation.

 

Large impacts on the early Earth: Where does the reducing power go?
Jonathan Itcovitz (Institute of Astronomy, University of Cambridge), Auriol S.P. Rae, Thomas M. Davison, Gareth S. Collins, Oliver Shorttle

Reduced surface environments are required for many prebiotic chemical pathways. Large impacts onto Hadean Earth have been suggested as scenarios able to generate such environments on a global scale. Physical and chemical processes that occur shortly after impact can, however, limit the reducing power that is available at planet surface. Here, we present impact simulations and chemical calculations that demonstrate the efficient loss of reducing power from the post-impact planetary surface. This loss occurs via the dynamic escape of impactor core material, or the sinking of this material to the planet core, during impact, and through interactions between the atmosphere and the impact-generated melt phase. We suggest that post-impact surface environments are sufficiently reduced that species important to prebiotic chemistry can form (e.g., HCN, HCCCN). Additionally, the formation of a reduced impact-generated melt phase allows for reducing power to be stored in the planet mantle, where it can degas to the surface on geologic timescales.

 

Giant planet formation around host stars of different masses
Heather Johnston (University of Leeds), Dr Olja Panic, Dr Beibei Liu

We carry out a pebble-driven planet formation simulations to investigate the formation of giant planets around intermediate-mass stars, in the stellar mass range between 1.5 M_sun and 3 M_sun. We find that the massive giant planets are preferred to emerge in the circumstances when the disks have larger sizes, metallicities, and/or higher disk accretion rates. As these properties are only enhanced with stellar mass, an alternative physical scenario is needed to explain the decline of giant planet frequency from 2 to 3 M_sun. We propose that FUV/EUV photoevaporation in this stellar mass range plays a role in actively removing the disc, and slowing down planet formation. This photoevaporation mechanism is only dominant after the first 2Myr, meaning that, in this scenario, giant planets form predominantly later than the first couple of Myr of disc evolution. This is not in contradiction with the ~2Myr disc lifetimes found observationally, because only a small fraction of stars (long-lived discs) end up becoming giant planet hosts.

 

Constraints on the timing of cometary bombardment relative to Earth's growth
Sarah Joiret (CNRS - Laboratoire d'Astrophysique de Bordeaux)

Isotopic signatures of Xe are different in the mantle and in the atmosphere of the Earth. While mantle Xe is chondritic (Peron Moreira, 2018; Broadley et al., 2020), atmospheric Xe would have evolved from the so-called primordial U-Xe, which is a mixture of ~ 80% chondritic Xe and ~ 20% cometary Xe (Marty et al., 2017). This naively suggests that the cometary bombardment only happened after the Earth was fully formed. The bombardment of comets is thought to have been triggered by the giant planet instability (Gomes et al., 2005) early in the history of the solar system. The timing of this instability is still uncertain (Morbidelli et al., 2018), but recent simulations seem to favour a very early instability (Clement et al., 2018). We present our ongoing project to constrain the timing of cometary bombardment relative to Earth's growth, using numerical simulations on one hand, and laboratory isotopic measurements of meteorites on the other hand.

 

Giant Exoplanets around M dwarf Stars
Shubham Kanodia (Carnegie Institution for Science, Earth and Planets Lab)

In this presentation, we describe the new Giant Exoplanets around M dwarf Stars (GEMS) survey initiated to to understand giant planets transiting around M dwarf stars. This survey will try to understand giant planet formation, by shedding light on big planets around small stars. We will perform a systematic search for these planets in the TESS full frame images, and continue our radial velocity follow up to confirm these planets and measure their masses. As part of this ongoing effort, we have confirmed about half the known Jovian planets around M dwarf stars and plan to triple this sample in three years. This increased sample will be crucial to estimate the TESS detection sensitivity, and thereby quantify the occurrence of these planets as a function of stellar and orbital parameters. Next, we describe how the existence of some of these planets stretches our understanding of planet formation, and necessitates revisiting the mass budget of class II protoplanetary disks. Finally, we discuss how these planets around cool stars with large transit depths are excellent targets for atmospheric characterisation for JWST and ARIEL, especially for equilibrium temperatures conducive to the existence of methane in planetary atmospheres. Through this presentation, we hope to encourage dialogue about planet formation, tidal evolution, atmospheric characterization and RV mass measurements in a hitherto (largely) unexplored regime of planets.

 

The Possible Formation of Jupiter from Supersolar Gas
Olivier Mousis (Aix Marseille Université, Institut Origines, CNRS, CNES, LAM, Marseille, France), Artyom Aguichine, and Jonathan Lunine

More than two decades ago, the Galileo probe performed in situ measurements of the composition of Jupiter's atmosphere and found that the abundances of C, N, S, P, Ar, Kr, and Xe were all enriched by factors of 1.5-5.4 times their protosolar value. Juno's measurements recently confirmed the supersolar N abundance and also found that the O abundance was enriched by a factor 1-5 compared with its protosolar value. Here, we aim at determining the radial and temporal evolution of the composition of gases and solids in the protosolar nebula (PSN) to assess the possibility that Jupiter's current composition was acquired via the direct accretion of supersolar gases. To do so, we model the evolution of a 1D α-viscous accretion disk that includes the radial transport of dust and ice particles and their vapors, with their sublimation and condensation rates, to compute the composition of the PSN. We find that the composition of Jupiter's envelope can be explained only from its accretion from PSN gas (alpha <= 10-3), or from a mixture of vapors and solids (alpha > 10-3). The composition of the PSN at 4 au, namely between the locations of the H2O and CO2 icelines, reproduces the one measured in Jupiter between 100 and 300 kyr of disk evolution. Our results are found to be compatible with both the core accretion model, where Jupiter would acquire its metallicity by late accretion of volatile-rich planetesimals, and the gravitational collapse scenario, where the composition of proto-Jupiter would be similar to that of the PSN.

 

An unbiased NOEMA 2.6 to 4 mm survey of the GG Tau ring
Thi Phuong Nguyen (Korea Astronomy and Space Science Institute), A. Dutrey, E. Chapillon, S. Guilloteau , J. Bary, T. L. Beck, A. Coutens , O. Denis-Alpizar, E. Di Folco, P. N. Diep , L. Majumdar , J.-P. Melisse, C.-W. Lee , V. Pietu, T. Stoecklin , and Y.-W. Tang

We will present the chemical content of the protoplanetary disk (PPD) surrounding GG Tau A, a well-known triple T Tauri system. Using NOEMA, we detected 17 molecules in the circumbinary disk of GG Tau A, with H2S and CCS were detected for the first time in a PPD. We analysed the data with a radiative transfer code to derive molecular densities and the abundance relative to 13CO, which we compare to those of the TMC1 cloud and LkCa 15 disk. The analysis confirms that sulphur chemistry is not yet properly understood. The D/H ratio, derived from DCO+/HCO+, DCN/HCN, and DNC/HNC ratios, points towards a low temperature chemistry. The detection of the rare species such as H2S and CCS confirms that GG Tau is a good laboratory to study the protoplanetary disk chemistry.

 

Protoplanetary disks components contained in pristine carbonaceous chondrites
Josep M. Trigo-rodríguez (Institute of Space Sciences (CSIC-IEEC)), Jordi Ibáñez-Insa

An overview of the rock-forming materials of carbonaceous chondrites will be presented. The intention is summarizing the different approaches to study them and infer valuable clues on the size, composition and properties of the materials forming protoplanetary disks.

 

Signatures of violent dynamical histories in the architectures of planetary systems
Diego Turrini (INAF), Angelo Zinzi

The dynamical history of planetary systems is recorded by their architectures through the dynamical excitation of the orbits of their planets. Studies have shown the existence of an anti-correlation between the number of planets in a system, i.e. its planetary multiplicity, and the eccentricity of their orbits. Such a trend suggests more violent dynamical histories for planetary systems currently observed to host fewer planets than for systems, like the Solar System, hosting a larger number of them. Orbital eccentricity, however, is only one piece in the mosaic of planetary architectures. Here we show how information on the dynamical past of planetary systems can be more reliably extracted from their architectures using the simple metric provided by the Normalized Angular Momentum Deficit (NAMD). The NAMD metric, already used in the study of the Solar System, offers a fast and efficient way to quantify and compare the global dynamical excitation of planetary systems even when their architectures are quite different. Its use confirms that the eccentricity-multiplicity anti-correlation reflects the underlying dynamical excitation-multiplicity anti-correlation. Using well-studied systems like Trappist-1 and the Solar System itself as reference benchmarks, the NAMD can be used to build a global 'dynamical excitation' scale that makes it easier to ascertain whether the dynamical history of planetary systems are governed by chaos or order.

 

planetary system architecture, dynamics, stability

 

Planetary Orbit Eccentricity Trends (POET). I. The Eccentricity-MPetallicity Trend for Small Planets Revealed by the LAMOST-Gaia-Kepler Sample
Dongsheng An (Nanjing University), Dong-Sheng An, Ji-Wei Xie , Yuan-Zhe Dai , and Ji-Lin Zhou

Orbital eccentricity is one of the basic planetary properties, whose distribution may shed light on the history of planet formation and evolution. Here, in a series of works on Planetary Orbit Eccentricity Trends (dubbed POET), we study the distribution of planetary eccentricities and their dependence on stellar/planetary properties. In this paper, the first work of the POET series, we investigate whether and how the eccentricities of small planets depend on stellar metallicities (e.g., [Fe/H]). Previous studies on giant planets have found a significant correlation between planetary eccentricities and their host metallicities. Nevertheless, whether such a correlation exists in small planets (e.g. super-Earth and sub-Neptune) remains unclear. Here, benefiting from the large and homogeneous LAMOST-Gaia-Kepler sample, we characterize the eccentricity distributions of 244 (286) small planets in single (multiple) transiting systems with the transit duration ratio method. We confirm the eccentricity-metallicity trend that eccentricities of single small planets increase with stellar metallicities. Interestingly, a similar trend between eccentricity and metallicity is also found in the radial velocity (RV) sample. We also found that the mutual inclination of multiple transiting systems increases with metallicity, which predicts a moderate eccentricity-metallicity rising trend. Our results of the correlation between eccentricity (inclination) and metallicity for small planet support the core accretion model for planet formation, and they could be footprints of self (and/or external) excitation processes during the history of planet formation and evolution

 

The COPAINS Survey: directly imaging planetary and sub-stellar companions to accelerating stars
Mariangela Bonavita (The Open University), C. Fontanive, R. Gratton, K. Muzic

The last decade of direct imaging (DI) searches for sub-stellar companions has uncovered a widely diverse sample that challenges the current formation models, while highlighting the intrinsically low occurrence rate of wide companions, especially at the lower end of the mass distribution. These results clearly show how blind surveys, crucial to constrain the underlying planet and sub-stellar companion population, are not an efficient way to increase the sample of DI companions. It is therefore becoming clear that efficient target selection methods are essential to ensure a larger number of detections. In this poster I will present the results of the COPAINS Survey conducted with SPHERE/VLT, searching for sub-stellar companions to stars showing significant proper motion differences between different astrometric catalogues. With 10 companions detected, including 2 new BDs and two new potentially planetary-mass companions, and a sub-stellar companions detection rate of~20%, significantly higher than any blind survey, COPAINS is the most successful DI survey to date. This poster also introduces FORECAST (Finely Optimised REtrieval of Companions of Accelerating STars), a tool which allows to check the agreement between position and mass of the detected companions with the measured astrometric signatures, and was one of the key factor contributing to the success of the survey.

 

Planetary systems architecture and Earth-like planet prediction
Jeanne Davoult (Universität Bern), Lokesh Mishra, Yann Alibert

The detection of Earth-like planets is both one of the major goals of planetology and at the same time one of the most challenging. Earth-like planets are small and habitable zones, depending on the mass of the central star, can be far from the star, making difficult the detection of such planets and implying a lot of observation time with the current detection methods. Understanding the formation pathway and the architecture of planetary systems harboring an Earth-like planet could facilitate their detection. In this work, a way to identify systems, which are likely to harbor an Earth-like planet, is presented. This can help the selection of targets and can be used to optimize observational surveys. Using correlations in synthetic planetary systems, between planets themselves, or between planets and stellar parameters, the occurrence of Earth-like planets among systems is studied and typical architectures of systems hosting an Earth-like planet are defined. A random forest classifier is then used to classify system, and infer whether a planetary system harbors an Earth-like planet or not, based on its observable characteristics (e.g. properties of already observed planets). The same classifier allows identifying correlations between planets in the same system.

 

Analysis of Serendipitous Ion Tail Crossings of Comet 73P/Schwassmann-Wachmann 3
Samuel Grant (University College London), Prof. Geraint Jones, Prof. Antoinette Galvin

Volatile gases ejected from beneath a comet's surface are ionized when in the inner Solar System, transported by the solar wind through the Solar System, and are partially visible as an ion tail. In-situ encounters with cometary plasma provide unique information on the composition and behaviour of the comet, sometimes at significant distance from the comet nucleus. Serendipitous ion tail encounters by spacecraft occur surprisingly frequently, but are often missed due to the ambiguity of in-situ plasma measurements. Comet 73P/Schwassmann-Wachmann 3 now consists of an extended debris field along its orbit - a dust trail - having undergone fragmentation multiple times in the past few decades. In May-June 2006, fragments of comet 73P passed sunward of spacecraft ACE and Wind, both stationed at Sun-Earth L1. A flux of cometary pickup ions was recognised by Gilbert et al. (ApJ 815, 12, 10pp, 2015) in the ACE/SWICS and Wind/STICS datasets. Here, we use a method that provides relatively accurate information on serendipitous spacecraft-comet encounters to show that these detected ions most likely originated in the extended coma of the debris field trailing behind the larger fragments of 73P, rather than associated with the nucleus fragments themselves. This method uses the solar wind velocity measurements made by the spacecraft to extrapolate the flow of the solar wind back to the Sun, so that the likelihood of the solar wind flow transporting material from the comet to the spacecraft can be measured. In August 2011, Comet C/2010 X1 (Elenin) passed directly sunward of spacecraft STEREO-B. During this period, there was a flux in water-group cometary ions detected by STEREO-B/PLASTIC, identified as an ion tail encounter by Galvin et al. (AGU Fall Meeting 2013, abstract P31A-1789, 2013). Using proton velocities measured by STEREO-B/PLASTIC, a previously unknown ion tail crossing of comet 73P fragment AM is identified 3 weeks after the comet Elenin tail crossing, using the same method as for the ACE and Wind encounter. Encounters with recently fragmented comets such as 73P provide opportunities to measure pristine interior material indirectly through the transportation of cometary ions via the solar wind.

 

Towards completing extrasolar systems with the TROY project
Jorge Lillo-Box (Center for Astrobiology (CAB)), O. Balsalobre-Ruza

In this poster I will provide an overview of the status of our TROY project aiming at detecting and constraining the presence of co-orbital planets/bodies in extrasolar systems. Co-orbitals do exist in our Solar System in the form of small (max- 400 km in size) asteroids trapped in the Lagrangian points of six out of the eight planets. However, planet formation theories allow their formation up to planetary sizes and dynamical stability confirms these 1:1 resonances are indeed stable in the long-term. Exploring these configurations has remained in the to-do list of the exoplanet exploration. With the TROY project we aim at filling this gap from an observational point of view with strong implications in planet formation and evolution. The first conclusions of the project will be presented.

 

The KOBE experiment: filling the habitable zone desert in late K-dwarfs
Jorge Lillo-Box (Center for Astrobiology (CAB)), A. Castro-González

The absence of confirmed planets within the habitable zone of late-type K-dwarfs (effective temperatures in the range 3800-4600 K) is potentially due to an observational bias. While missions like Kepler (and ground-based RV surveys like HARPS) have focused on Solar-like stars, other surveys like CARMENES, MEarth, TRAPPIST or SPECULOOS are focusing on the lowest mass potential planet hosts, M-dwarfs. However, K-dwarfs represent a unique opportunity in the astrobiological context. These stars are more quite in terms of extreme radiation than their lower-mass counterparts and have less activity RV noise than the G-dwarfs. Their habitable zones are neither too far to difficult planet detection (like G-dwarfs) nor too close to have the HZ planet tidally locked (like M-dwarfs). The KOBE experiment is a RV survey using the CARMENES instrument at Calar Alto observatory to monitor 50 late K's and proof this apparent observational gap. In this poster, we will present the first results of the survey.

 

Modelling of solar and stellar brightness variations
Nina-Elisabeth Nemec (Universität Göttingen)

The emergence of magnetic field on stellar surfaces leads to the formation of magnetic features, such as dark spots and bright faculae. The expected facular and spot signals in stellar data are quite different, as they have distinct temporal and spectral profiles. The plethora of photometric data obtained by past and current space missions, plus the high precision transmission spectroscopy data brought by the James Webb Space Telescope have underlined the needs for a better understanding and modelling of stellar brightness variations on various timescales. Here we present various modelling efforts that have allowed to understand solar brightness variations in the broader context of stellar variability. To model the magnetic component of the variability we follow the SATIRE approach of calculating brightness variations, which was shown to reproduce the solar variability in great detail. We connect variability of the Total Solar Irradiance (i.e. the spectral integrated solar flux) to that measured in various spectral passbands, routinely used in broad-band photometry (e.g., CoRoT, Kepler, TESS. etc). Recent simulations with the 3D MHD radiative code MURaM made it also possible to calculate variability of spectral solar irradiance brought by the granulation which dominates total variability on timescales below about a day. By combining calculations of spectral solar irradiance variability brought by magnetic features and granulation we obtain a model capable of returning variability on timescales from minutes to decades. Currently, massive efforts are put into extending these calculations to stars with various values of metallicity and effective temperature.

 

An update on the young V1298 Tau system as observed by CHEOPS, HST and Spitzer
Hinna Shivkumar (University of Amsterdam), Hinna Shivkumar, Jean-Michel Désert, Saugata Barat, Georgia Mraz, Bob Jacobs, Vatsal Panwar, James Sikora, John Livingston, Trevor David, Lorenzo Pino, Erik Petigura

Young planets form a unique bridge between planet-forming protoplanetary disks and mature planets. In order to infer the internal and atmospheric structure of these young inflated planets, it becomes important to have high-precision measurements of their mass and radius. The V1298 Tau system, only a mere 23 Myrs old, is a keystone multi-planetary system hosting four transiting planets. Since the planets orbit a highly variable star, constraining the mass of the planets using radial velocities becomes a challenge. In such a scenario, using transit-timing variations (TTVs) provides another avenue to constrain the mass of the planets. In this poster, I will present high-precision transit observations of the first three planets in the V1298 Tau system using the CHEOPS telescope. I will provide an insight into the data analysis methodology used to encounter the unique systematics of CHEOPS. I will also briefly discuss the decorrelation methods used to tackle stellar variability evident in the observations. Finally, I will present the improvement in the transit parameters of the three young planets, place these observations in the context of HST and Spitzer observations of this system, and how these observations will help in constraining the mass of the planets using TTV models. Furthermore, I will discuss the implications of these measurements in terms of formation and early evolution of sub-Neptune planets.

 

Planets Across Space and Time (PAST) IV: The Occurrence and Architecture of Kepler Planetary Systems as a Function of Kinematic Age Revealed by the LAMOST-Gaia-Kepler Sample
Jia-Yi Yang (Nanjing University), Jia-Yi Yang, Di-Chang Chen, Ji-Wei Xie, Ji-Lin Zhou, Subo Dong, Zi Zhu, Zheng Zheng, Chao Liu, Weikai Zong, Ali Luo

One of the fundamental questions in astronomy is how planetary systems form and evolve. Measuring the planetary occurrence and architecture as a function of time directly addresses this question. In the fourth paper of the Planets Across Space and Time (PAST) series, we investigate the occurrence and architecture of Kepler planetary systems as a function of kinematic age by using the LAMOST-Gaia-Kepler sample. To isolate the age effect, other stellar properties (e.g., metallicity) have been controlled. We found the following results. (1) The fraction of stars with Kepler-like planets (FKep) is about 50% for all stars; no significant trend is found between FKep and age. (2) The average planet multiplicity (Np) exhibits a decreasing trend ( ∼2σ significance) with age, which decreases from Np ∼ 2.6–2.7 for stars younger than 1 Gyr to Np ∼1.8–20 for stars older than 8 Gyr. (3) The number of planets per star (η=FKep × Np) shows a more pronounced decreasing trend (∼3σ significance), which decreases from η ∼ 1.4–1.5 for young stars to η ∼ 0.9–1.0 for old stars. (4) The median mutual orbital inclination of the planets (σi,k) increases from 2.2 to 3.9 degree as stars aging, and the Solar System also fit such a trend. The nearly independence of FKep ∼ 50% on age implies that planet formation is robust and stable across the Galaxy history. The age dependence of Np and σi,k demonstrates planetary architecture is evolving, and planetary systems generally become dynamically hotter with fewer planets as they age.

 

Investigating Possible Orbital Variations from Exoplanet Transit Databases
Li-Chin Yeh (National Tsing Hua University / Institute of Computational and Modeling Science ), Ing-Guey Jiang

A huge number of mid-transit times from ExoClock and TESS projects are employed to investigate the possible non-linear transit timing variations of exoplanets by performing data-model fitting with both the fixed orbit and the orbital variation models. Several exoplanets in favor of orbital decay are found. Their tidally evolutionary orbits are also studied and presented.

 

Stellar/solar activity and interaction with planet; Exoplanet ground-based observations

 

The HADES RV Programme with HARPS-N@TNG-HADES: THE HArps-n red Dwarf Exoplanet Survey
Laura Affer (INAF - Osservatorio Astronomico di Palermo), Affer Laura & the HADES Team

Many efforts to detect Earth-like planets around low-mass stars are currently devoted to almost every extra-solar planet search. M dwarfs stand as ideal targets for Doppler radial velocity searches as their lower masses and luminosities make low-mass planets orbiting within their habitable zones more easily detectable than those around higher-mass stars. Nonetheless, the statistics of the frequency of this kind of planet hosted by low-mass stars remains poorly constrained. Our M-dwarf radial velocity monitoring with HARPS-N within the HARPS-N Red Dwarf Exoplanet Survey Radial Velocity (HADES) project started in 2012 and is contributing to the widening of the current statistics through the in-depth analysis of accurate radial velocity observations in a narrow range of spectral sub-types from M0 to M3, to investigate the planetary population around a well-defined class of host stars. The HADES project is the result of a collaborative effort between the Italian Global Architecture of Planetary Systems (GAPS) Consortium, the Institut de Ciències de l'Espai de Catalunya (ICE), and the Instituto de Astrofísica de Canarias (IAC). Two photometric programs regularly and almost simultaneously follow up the sample of M stars to characterize the stellar activity, to highlight periods that are due to chromospheric inhomogeneities modulated by stellar rotation and differential rotation, and thus to distinguish from the periodic signals those due to activity and to the presence of planetary companions. We present the complete analysis of the HADES survey and the results obtained concerning the statistical, activity, and characterization part and the planet revealing part, around M dwarfs.

 

Modelling the Effects of Stellar Magnetic Fields on (Exo)Planetary Magnetosphere - Atmosphere systems with Implications for Habitability
Sakshi Gupta (Indian Institute of Science Education and Research Kolkata), Sakshi Gupta, Arnab Basak and Dibyendu Nandy

The long-term evolution of stellar magnetic activity governs the environment of the orbiting planets impacting their habitability. We perform three-dimensional magnetohydrodynamic simulations followed by a detailed parameter space study to understand the effect of variation in stellar wind magnetic field and intrinsic magnetosphere on the planetary magnetic field topology and atmospheric mass loss rate. We find that the relative strength of the planetary magnetic field with respect to that of stellar wind plays a critical role in determining the steady-state magnetospheric configuration and atmospheric erosion. Either strengthening the stellar wind magnetic field or weakening the planetary magnetospheric strength results in stellar field accumulation in front of the planet, similar to that of an imposed magnetosphere. We explore the formation of Alfvén wings on the planetary night-side wake region at different magnetic activity levels. We identify reconnection processes and wind conditions that lead to the bifurcation of the current sheet in the magnetotail. With increasing stellar wind magnetic field strength, the day-side reconnection point approaches the planet, thereby increasing the mass-loss rate. Our model results are in line with analytic theory. Our study has far-reaching implications in the context of star-planet interaction and (exo)planetary habitability.

 

Astrospheres of Planet-Hosting Cool Stars and the Cosmic Ray Transport Within
Konstantin Herbst (Christian-Albrechts-Universität zu Kiel), L. R. Baalmann, F. Effenberger, N. E. Engelbrecht, S. E. S. Ferreira, K. Scherer, R. D. T. Strauss

Thanks to dedicated long-term missions like Voyager and GOES over the past 50 years, much insight has been gained into the activity of our Sun, the solar wind, its interaction with the interstellar medium, and, thus, the formation, the evolution, and the structure of the heliosphere. With the help of multi-wavelength observations by the Hubble Space Telescope, Kepler, and TESS, we could detect a variety of extrasolar planets and exomoons and study the characteristics of their host stars and thus became aware that other stars drive bow shocks and astrospheres. Although features like, e.g., stellar winds, so far can not be measured directly, over the past years, several techniques have been developed to indirectly derive properties like stellar mass-loss rates and wind speeds, information that can be used as direct input to existing astrospheric modeling codes. Here we present our astrospheric modeling efforts (3D (magneto-)hydrodynamic) of Proxima Centauri and LHS1140. In the case of the heliosphere, the propagation of Galactic cosmic rays (GCRs) and their relevance in the context of planetary habitability is well understood; however, it is poorly studied when it comes to M stars. Here we further show our latest 1D and 3D transport model efforts of the GCR flux at Proxima Centauri b and LHS1140 b and briefly discuss the possible impact of turbulence.

 

PLATOspec an UV optimized, high-resolution spectrograph in the southern hemisphere for exoplanet research.
Petr Kabath (Astronomical Institute of the Czech Academy of Sciences), Eike W. Guenther, Leonardo Vanzi, Artie Hatzes, Rafael Brahm, Jan Janí­k

After the discovery phase of exoplanet research, the aim is now to understand their structure and evolution. Two new satellite missions are now on the horizon: PLATO and ARIEL. PLATO aims to discover planets down to the size of the Earth, and out to the habitable zone in a solar-like star. In contrast to previous missions, PLATO will not only detect the planets but also characterise them by determining their radii, and ages precisely. An integral part of the mission is the mass-determination using RV-measurements obtained with ground-based telescopes. Unfortunately, many solar-like stars are too active to detect an Earth-like planet in the habitable zone. It is thus necessary to characterise the stars first. Particularly important is to find out how active the stars are, because low-mass planets in wide orbits can only be detect in inactive stars. It is thus necessary to monitor the PLATO targets in the CaII HK-lines before taking many ultra-high precision RV-measurements of them. Furthermore, almost all low-mass planets are in systems. Perhaps many of them even have outer gas-giants. We also need to know if this is the case, and we must exclude binaries. These are the two first aims of the PLATOspec project. PLATOspec is a new, fibre-fed high resolution Echelle spectrograph at the ESO1.5m telescope that will be dedicated to PLATO follow-up observations. The ARIEL mission aims to study the atmospheres of 1000 hot and warm planets. To select the best targets for ARIEL, it is necessary to determine not only the radii of the planets but also their masses. This is necessary, because the extend of the atmosphere of a planet, and thus the strength of the signal from the atmosphere, depends on it. Characterizing warm, and hot planets with extended atmospheres is the third science goal of PLATOspec.

 

Hydrodynamical modelling of the escaping atmospheres of planets around evolved stars
Thomas Konings (Insitute of Astronomy, KU Leuven), Leen Decin

Planets that orbit low- to intermediate stars will experience vigorous star-planet interactions when their host star evolves through the giant branches, including the Asymptotic Giant Branch (AGB) phase. Alongside the evolution of the orbit, the physical and chemical state of the planet's atmosphere will be affected by the intense radiation and outflow of the AGB star. Until now, the description of atmospheres of planets around evolved stars was limited to analytical expressions that varied from Bondi-Hoyle-Lyttleton accretion of stellar wind material to an energy-limited approximation of hydrodynamical atmospheric mass loss. To properly assess the photoevaporative mass loss of such planets, one needs a numerical approach where heating due to photoionization is computed self-consistently during the integration of the hydrodynamical equations. We present here hydrodynamic models of gaseous planets around a Sun-like AGB star that take into account AGB stellar radiation. Subsequently, we estimate the impact of stellar wind ram pressure on the outflow of the planetary atmosphere.

 

Radar Blackouts at Mars: Evidence for a low altitude ionisation layer
Mark Lester (University of Leicester), Beatriz Sanchez-Cano, Dikshita Meggi, Simon Joyce, Katerina Stergiopoulou, Hermann Opgenoorth, Robert Lillis, Olivier Witasse, Roberto Orosei, and Marco Cartacci

Radars in orbit around Mars such as MARSIS on Mars Express and SHARAD on Mars Reconnaissance Orbiter provide evidence for the nature of the surface and some sub-surface layers. The MARSIS instrument also operates in a topside sounding mode, the Advanced Ionospheric Sounder (AIS) mode, which also receives surface reflections and we now investigate the impact of the solar energetic particles on the surface reflection during ionospheric sounding observations made by MARSIS. We present observations during December 2014 when MARSIS AIS was making observations on the nightside as Mars Express moved towards periapsis and then towards the dayside. Nightside AIS observations clearly demonstrate a similar loss of the surface signal to that seen in the MARSIS sub-surface mode. In addition there is evidence of a reflection from an enhanced layer created by the electrons which is responsible for the attenuation in the signal. The critical frequency is of order 1 MHz, which is equivalent to a peak electron density of order 10**10 m**-3, at an altitude of about 100 km. These characteristics are similar to our previous modelling work of the impact of the solar energetic electrons.

 

Mass Constraints of Young Proto-sub-Neptunes: Disentangling V1298 Tau's Planetary and Stellar Activity Radial Velocity Signals with MAROON-X
James Sikora (Anton Pannekoek Institute for Astronomy, University of Amsterdam), Jason Rowe, Saugata Barat, Jacob Bean, Jean-Michel Désert, Adina Feinstein, Emily Gilbert, Gregory Henry, David Kasper, Déreck-Alexandre Lizotte, Michael Matesic, Vatsal Panwar, Andreas Seifahrt, Hinna Shivkumar

Planets orbiting young stars (<100 Myr) serve as important windows into the early stages of planet formation and evolution. When coupled with known ages and insolation fluxes, bulk density measurements of young planets can be used to infer the core compositions and masses of their primordial H/He-dominated atmospheres. Additionally, precise mass constraints of such planets provide the unique opportunity to test initial planet formation theories and theories of atmospheric mass loss processes. The 20-30 Myr old T-Tauri star, V1298 Tau (V = 10 mag), hosts 4 super-Neptune to Jupiter-sized transiting planets. Depending on the assumed stellar activity and planet masses, they are expected to evolve into super-Earths/sub-Neptunes that bound the radius valley. Here we present a joint analysis of high-precision photometry (K2, TESS) and high-precision radial velocities (MAROON-X, HARPS-N, CARMENES) carried out in order to constrain the masses of these young planets and compare with formation and evolution theories of gas-rich planets.

 

A new tool for precise radial velocity measurements
Michaela Vítková (Masaryk University), Jana Köhler, Mathias Zechmeister, Marek Skarka

One of the most cost-effective, accurate, and cheap methods for radial velocity measurements is the usage of the gas absorption cell (e.g., Iodine cell) method. We present new open-access software for processing spectra obtained with gas cells, the python-based program Viper (Velocity and IP EstimatoR), and recent results obtained with it. It can be used for data obtained with gas cell from multiple instruments (e.g., OES, TCES, CRIRES+) and new can be easily added. When this method was tested on Ondrejov Echelle Spectrograph data, the achieved rms improved 6 times compared to a classic cross-correlation method. Viper is still under development. One of the new features we are currently working on is employing telluric lines that allow us to use Viper for the analysis without a gas cell.

 

Ionospheres, magnetospheres, plasma environment

 

Impact of the precipitation of magnetospheric electrons on the composition of Triton's atmosphere
Benjamin Benne (Laboratoire d'Astrophysique de Bordeaux), Bilal Benmahi, Michel Dobrijevic, Thibault Cavalié, Jean-Christophe Loison, Kevin Hickson, Mathieu Barthélémy, Jean Lilensten

Introduction Triton is the biggest satellite of Neptune. It was only visited by Voyager 2 in 1989. During this mission, a surprisingly dense ionosphere was observed (Tyler et al. 1989), denser than the one of Titan despite being three times farther from the Sun. Thus, an additional source of ionization seems required. As energetic electrons were detected in Neptune's magnetosphere by the LECP instrument on board Voyager 2 (Krimigis et al. 1989), they could provide the needed additional power to Triton's atmosphere (Krasnopolsky et al. 1993). Therefore, we coupled a photochemical model of Triton's atmosphere with an electron transport code to study how these electrons could impact Triton's atmospheric chemistry. Methodology We used the most recent photochemical model of Triton's atmosphere from Benne et al. (2022) and coupled it with the electron transport code TRANS (see Gronoff et al. (2009a) and references therein). The photochemical model produces an initial atmosphere that is used by TRANS to compute the propagation of magnetospheric electrons inside it. The input precipitation is based on the work of Strobel et al. (1990), using data from the LECP instrument presented in Krimigis et al. (1989). We also tested a modified precipitation flux following the recommendations of Sittler & Hartle (1996), whose calculations suggest that the precipitation of low energy electrons may be strongly inhibited. The outputs of TRANS are then used in the photochemical model to compute the reactions rates of the electron impact-ionization and -dissociation reactions. Iterations between the two codes are performed until steady state is reached. Once the nominal composition of Triton's atmosphere is determined, we ran a Monte Carlo simulation to study the impact of chemical uncertainties on our results. Results Benne et al. (2022) used the ionization profile from Strobel et al. (1990) to take into account the precipitation of magnetospheric electrons but failed to match the electronic number density profiles measured by Voyager 2 from nearly one order of magnitude, even with chemical uncertainties. Coupling this model to TRANS allows us to find results that are in close agreement with those observations. It also permits us to better understand the impact of the different input parameters (input precipitation, magnetic field strength, field line incidence, orbital mean) on the atmospheric chemistry. With this work, the electronic number density maximum is not due to electronic precipitation but to the ionization by EUV photons, in contrast to the results of Benne et al. (2022), Krasnopolsky & Cruikshank (1995) and Strobel & Summers (1995).

 

Seasonal variation of neutral gases in Titan's ionosphere
Maélie Coutelier (LATMOS / CNRS), Thomas Gautier, Koyena Das, Joseph Serigano

With 13 years of observations, the Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft has observed the upper atmosphere of Titan through two seasons: winter and spring. The complex atmosphere is mainly composed of N2, CH4, H2 and Ar, but a lot more carbon and nitrogen bearing trace species have been observed by INMS and other instruments. Using data from the closed source neutral mode of INMS instrument, we studied the abundance and variation of neutral species in Titan ionosphere, between 1500 and 950 km of altitude. We will present an ongoing effort on the reanalysis of the entire INMS Titan's observation dataset. We recalibrated INMS data by taking into account the dead time correction, the ram pressure enhancement, the saturation correction, the increase of pressure in the chamber with the decreases of altitude, the sensitivity and the contamination by thruster firing (Cui et al., 2009,2012). In addition, species entering the instrument were ionized and fragmented into ions inside INMS chamber, making difficult the identification of different species in such complex mass spectra. To retrieve the molecular mixing ratios we used a Monte-Carlo sampling on the fragmentation pattern to deconvolve the signal. To obtain a complete mass spectrum (m/z 1 to 99), we stacked INMS data, which increases the incertitude on the altitude. We used the mass spectra deconvolution code developed by Gautier et al., (2020), also employed by Serigano et al., (2020) when they treated Saturn INMS data. This enabled the retrieval of vertical and seasonal variation of Titan's atmosphere major components. Our results show the strong influence of the solar activity on the gases mixing ratio variations (Shebanits et al, 2017 ; Westlake et al., 2014). We also derived the N2 and CH4 density from our results (Muller Wodarg et al., 2008).

 

Utilising light ion measurements to derive mixing ratios of heavier neutral species in Saturn's ionosphere and addressing open questions with light ion chemistry
Joshua Dreyer (Swedish Institute of Space Physics (IRFU), Uppsala University), Erik Vigren, Fredrik L. Johansson, J. Hunter Waite

During Cassini's Grand Finale in 2017, the number densities of electrons and light ions in Saturn's ionosphere were measured in situ. Light ion chemistry and density measurements can be utilised to derive mixing ratios for heavier neutral species, such as water and methane, which we compare to recent estimates and measurements from other studies. Furthermore, we show that electron data from the Langmuir Probe and light ion densities from the Ion and Neutral Mass Spectrometer (INMS) correlate very well after correcting the INMS timestamps as outlined in Dreyer et al. (2022, PSJ). This may serve cross-calibration purposes and be of further use to constrain the abundance of heavier ions and address open questions in regard to light ion chemistry.
​

BepiColombo 2nd Mercury flyby: ion composition measurements from the Mass Spectrum Analyzer
Lina Hadid (LPP /CNRS - École Polytechnique), MSA/MPPE Team

On June 23rd 2022, BepiColombo performed it’s second gravity assist maneuver (MFB2) at Mercury. Just like the first encounter which took place on October 1 2021, the spacecraft approached the planet from dusk-nightside to dawn-dayside to an extremely close distance within about 200 km altitude above the planet’s surface. This distance is closer than the two orbiters of BepiColombo will orbit the planet after the orbit insertion in 2025. Eventhough BepiColombo is in a so-called “stacked configuration” during cruise, meaning that the instruments cannot yet be fully operated, the instruments can still make interesting observations. Particularly, despite their limited field-of-view, the particle sensors will allow us to get a hint on the ion composition and the dynamics very close to the planet. In this presentation, we will present the first observations of the Mass Spectrum Analyzer (MSA) at Mercury during MFB2. MSA is part of the low energy sensors of the Mercury Plasma Particle Experiment (MPPE, PI: Y. Saito), which is a comprehensive instrument package for plasma, high-energy particle and energetic neutral atom measurements (Saito et al. 2021), onboard the Mercury Magnetospheric Orbiter (Mio). MSA is a time-of-flight spectrometer that provides information on the plasma composition and the three-dimensional ion distribution functions up to a somewhat larger energy ~ 38 keV/q and masses from ~ 1-60 amu (Delcourt et al. 2016). We will focus on the ion composition during 1) the closest approach which occurred around 09:44 UT and on the outbound orbit in the 2) foreshock region between ~10:00 UT and ~ 10:30 UT.

 

Solar Orbiter's Crossing of Comet Leonard's Ion Tail
Geraint Jones (UCL Mullard Space Science Laboratory, UK), Samuel Grant, Timothy Stubbs, Christopher Owen, et al.

In December 2021, ESA's Solar Orbiter spacecraft crossed the ion tail of comet C/2021 A1 Leonard, around 44.5 million km downstream of the nucleus. This event was predicted by co-author S. Grant. Here, we provide an overview of the circumstances of this fortuitous ion tail crossing, including how it had been predicted, and the relative geometry of the comet, tail, and Solar Obiter spacecraft. Comet Leonard was imaged extensively from the ground and also by some spacecraft. We show the results of our initial analysis of these Earth- and space-based images, and how they provide context for the Solar Orbiter tail crossing observations by the spacecraft's suite of in situ instruments. An overview is also provided of some of the data returned by the spacecraft, including the detection of the suspected weakened bow shock of the comet. We briefly discuss the implications of the results of the crossing in the context of other, similar events, and for the ESA Comet Interceptor mission, due for launch in 2029.

 

Exploring Plasma Asymmetries in Venus' Magnetosheath
Sebastián Rojas Mata (Swedish Institute of Space Physics, Kiruna), Gabriella Stenberg Wieser, Yoshifumi Futaana

Venus is a prime target for studying how magnetized plasma flows interact with atmospheric bodies in our Solar System or around other stars. Though similarly sized to Earth, it lacks an intrinsic magnetic field, leading to a close coupling of its magnetosphere to the solar wind. Conversely, while Venus and Mars share such coupling typical at unmagnetized planets, their different sizes cause other dissimilar interactions with the space plasma environment. Comparative analyses between these planets therefore enable us to investigate the physics of planetary magnetospheres. Here we focus on the proton plasma in Venus' magnetosheath, the intermediary region through which the solar wind transfers momentum and energy to the planet. Using data taken by Venus Express' (VEX's) Ion Mass Analyser (IMA) instrument, we statistically characterize the asymmetries in proton bulk parameters between different electromagnetic hemispheres of the dayside magnetosheath. Investigating such details of Venus' induced magnetosphere, especially when compared to similar studies at Earth and Mars, helps us understand how factors like spatial scale, turbulence, or pick-up ions influence planetary magnetosheaths.

 

NIRwave: A wave-turbulence-driven solar wind model constrained by Parker Solar Probe observations
Simon Schleich (University of Vienna), Sudeshna Boro Saikia, Udo Ziegler, Manuel Güdel, Michael Bartel

Stellar winds represent one of the essential phenomena shaping exoplanet atmospheres over evolutionary timescales. However, as the winds of solar analogues are very weak, we need to characterise them and the effects they have on exoplanet atmospheres through model descriptions of the solar wind. We present NIRwave, a solar wind model based on coupling the general MHD code NIRVANA to an explicit wave-turbulence-driven heating mechanism. Our model is constrained by observational data from the Parker Solar Probe (PSP). The adapted heating mechanism is based on the interaction and subsequent dissipation of counter-propagating Alfvén waves in the solar corona, accounting for a turbulent heating rate as a driving mechanism of the solar wind. The solar magnetic field is assumed to be an axisymmetric dipole. NIRwave is able to successfully reproduce the characteristic bimodal structure of the solar wind. Despite implementing simplified conditions representing the coronal magnetic field and initial parameters of the simulation domain, the parameters characterising our steady-state solution agree with previously established results and empirical constraints. In a comparison to a polytropic wind model based on the unmodified version of NIRVANA, we find that our NIRwave model is in better agreement with the observational constraints derived by us. As this model relies on simplified assumptions about the nature of the solar wind, it could be utilised to derive the wind parameters of a wide range of solar-type stars, including targets of upcoming exoplanet missions such as Ariel and PLATO.

 

Ionopause detections in the Martian ionosphere
Katerina Stergiopoulou (University of Leicester), Beatriz Sánchez-Cano, Mark Lester, Dikshita Meggi, Simon Joyce, David Andrews

The ionopause boundary at unmagnetised planets, such as Mars and Venus, separates the planetary ionospheres from the solar wind plasma. It is not always present in the Martian ionosphere and the conditions under which it is formed are not as well defined as in the Venus case. In this study we use MAVEN LPW observations to probe the dayside ionosphere of Mars and describe the structure of the ionopause and its formation and variability drivers. We identify the boundary as the location where we see electron density and temperature gradients as well as increased electron temperature fluctuations. Utilising several years of electron density and temperature measurements, we perform a statistical analysis of the ionopause detections with respect to their height and solar zenith angle, and we compare our findings with what is known about the ionopause at Venus to better understand the processes resulting in the ionopause formation at Mars. What is more, through observations from additional MAVEN and Mars Express instruments, we investigate how various factors, including the crustal fields and the upstream solar wind conditions, alter the characteristics of the ionopause formation.

 

Detecting solar energetic particle events and Forbush Decreases on Mars with an Error Detection and Correction counter
Shayla Viet (Norwegian University of Science and Technology (NTNU)), Shayla B.T. Viet, Elise W. Knutsen, Franck Montmessin, Olivier Witasse, Beatriz Sanchez-Cano, Mark Lester, Robert F. Wimmer-Schweingruber

The objective of this project was to detect and investigate space weather events around Mars over a longer continuous time period by using data from Mars Express which has been in orbit around Mars for almost 20 years. Monitoring space weather events is becoming increasingly important as we expand our presence at Mars, both on the surface and in orbit. In addition, we are becoming more and more dependent in our daily lives on Earth on satellites, which may be damaged by radiation. Mars is less protected than Earth from space weather events as the planet has a thinner atmosphere and no global intrinsic magnetic field, making radiation a challenge. In this project an algorithm was created to detect space weather events at Mars from data from an algorithm called Error Detection and Correction (EDAC). EDAC counters exist on all spacecraft, and monitor memory errors in onboard computers. The EDAC software is often active even when other instruments are turned off, providing engineers long uninterrupted timeseries. Charged energetic particles from Galactic Cosmic Rays (GCRs) and transient solar energetic particle (SEP) events are able to trigger an EDAC algorithm by penetrating the spacecraft and cause bit-flips on the physical memory cells in the onboard computers, which triggers the EDAC counter into incrementing. By obtaining a daily count rate from an EDAC on the Mars Express and correcting for the long-term variations of the GCR background radiation caused by the solar cycle modulation, numerous SEP events and Forbush Decreases, which are rapid and temporary declines of GCR intensity, in Mars orbit from Jan 2005 to Feb 2022 were identified.

 

habitability & exobiology

 

Introducing the concept of “astrobiological time-analogs”: Ecological successions throughout the desiccation of hypersaline lagoons on Earth and the wet-to-dry transition on early Mars
Alberto Fairén (Centro de Astrobiología), Nuria Rodríguez, Laura Sánchez-García, Esther Uceda, Daniel Carrizo, Patricia Rojas, Ricardo Amils, and Jose Luis Sanz

Early Mars most likely had a diversity of environments in terms of pH, redox conditions, temperature, geochemistry, and mineralogy. Field research in terrestrial analog environments contribute to understand the habitability of this diversity of environments on Mars in the past, because terrestrial analogues are places on Earth characterized by environmental, mineralogical, geomorphological, or geochemical conditions similar to those observed on present or past Mars. So far, analogs have been referred to terrestrial locations closely similar to any of the geochemical environments that have been inferred on Mars, i.e., they are "site-analogs" that represent snapshots in time: one specific environmental condition at a very specific place and a very specific time. Because of this, each individual field analog site cannot be considered an adequate representation of the changing martian environmental conditions through time. Here we introduce the concept of "astrobiological time-analog", referred to terrestrial analogs that may help understand environmental transitions and the related possible ecological successions on early Mars. As Mars lost most of its surface water at the end of the Hesperian, this wet-to-dry global transition can be considered the major environmental perturbation in the geological history of Mars, and therefore merits to be the first one to be assigned a "time-analog" for its better understanding and characterization. At the end of the Hesperian, several paleolakes on Mars were characterized by episodic inundation by shallow surface waters with varying salinity, evaporation, and full desiccation repeatedly over time, until the final disappearance of most surface water after the wet-to-dry transition. We show here that similar conditions can be tested through time in the terrestrial analog Tirez lagoon. Tirez was a small and seasonal endorheic athalassohaline lagoon that was located in central Spain. In recent years, the lagoon has totally dried out, offering for the first time the opportunity to analyze its desiccation process as a "time-analog" to similar events occurred during the wet-to-dry transition on early Mars. To do so, here we describe (i) the microbial ecology of Tirez when the lagoon was still active 20 years ago, with prokaryotes adapted to extreme saline conditions; (ii) the composition of the microbial community in the dried lake sediments today, in many case groups that thrive in sediments of extreme environments; and (iii) the molecular and isotopic analysis of the lipid biomarkers that can be recovered from the sediments today. We conclude that Tirez was habitable for a wide range of prokaryotes before and after its complete desiccation, in spite of the repeated seasonal dryness; and our results may inform about research strategies to search for possible biomarkers in Mars after all the water was lost. Our 25 yearlong analyses of the ecological transitions in the Tirez lagoon represent the first terrestrial astrobiological "time-analog" for desiccating saline lakes on early Mars.

 

Habitable zones in stellar binaries with circumbinary giant planets
Nikolaos Georgakarakos (New York University Abu Dhabi), Siegfried Eggl, Ian Dobbs-Dixon

Several stellar binary systems are known to host circumbinary planets. The so-called dynamically informed habitable zones are a valuable tool for evaluating the potential of a planet to have liquid water on its surface because they take into consideration the orbital evolution of the system as well as the actual stellar radiation received by the planet. In this work, we present an analytic method for calculating dynamically informed habitable zones in circumbinary systems and we explore whether such systems, which already have a planet, can host additional potentially habitable worlds. We apply our methodology to some of the Kepler circumbinary systems; more specifically to Kepler-34 and Kepler-38. We demonstrate that the presence of the known giant planets is not prohibitive for the existence of potentially habitable worlds.

 

Should the debate on the life in the clouds of Venus include acidophilic fungi?
Grzegorz P. Slowik (Institute of Materials and Biomedical Engineering, University of Zielona Gora, Poland), Anna Olewicz (Department of Immunology, Poznan University of Medical Sciences Poznan, Poland)

Venus and Earth are the most similar planets in the Solar System in terms of relative radius, accelaration of gravity and mean density [1]. Although present-day Venus is characterized by a very strong greenhouse effect, 3D-climate models suggest that this planet could have had hospitable climate and ocean of water on its surface [2]. The conditions supporting life include the presence of elements C, H, N, O, P, and S and solvents [3]. The lower cloud layer of Venus comprises favorable components for microbial life, including moderate temperatures, pressures, and the presence of micron-sized sulfuric acid aerosols [4]. Fungi metabolic versatility is well established, including metabolic pathways for sulfur assimilation [5]. Biofilms are the most abundant form of life in extreme environments including highly acidic ones, and acidophilic fungi are known components of biofilms, the most successful life strategy on the Earth. [6]. Fungi are also characterized by incredible ecological plasticity, remarkably tolerant to water-stress conditions, and possess outstanding ability to tolerate and even thrive in the most extreme environments [7]. References: [1] Taylor, Fredric W., Håkan Svedhem, and James W. Head. Venus: the atmosphere, climate, surface, interior and near-space environment of an Earth-like planet. Space Science Reviews 214 (2018):1-36. [2] Way MJ, Del Genio AD, Kiang NY, Sohl LE, Grinspoon DH, Aleinov I, Kelley M, Clune T (2016) Was Venus the first habitable world of our solar system? Geophys Res Lett 43:8376-8383. https://doi.org/ 10.1002/2016GL069790 3. Noam R. Izenberg, Diana M. Gentry, David J. Smith, Martha S. Gilmore, David H. Grinspoon, Mark A. Bullock, Penelope J. Boston, and Grzegorz P. Słowik. The Venus Life Equation Astrobiology 2021 21:10, 1305-1315 4. Sanjay S. Limaye, Rakesh Mogul, David J. Smith, Arif H. Ansari, Grzegorz P. Słowik, and Parag Vaishampayan. Venus' Spectral Signatures and the Potential for Life in the Clouds Astrobiology 2018 18:9, 1181-1198 5. Linder T. Assimilation of alternative sulfur sources in fungi. World J Microbiol Biotechnol. 2018;34(4):51. doi: 10.1007/s11274-018-2435-6. 6. . Hujslová M, Bystrianský ​​​​​, Benada O, Gryndler M. Fungi, a neglected component of acidophilic biofilms: do they have a potential for biotechnology? Extremophiles. 2019 May;23(3):267-275. doi: 10.1007/s00792-019-01085-9. 7. Coleine C, Stajich JE, Selbmann L. Fungi are key players in extreme ecosystems. Trends Ecol Evol. 2022 Jun;37(6):517-528. doi: 10.1016/j.tree.2022.02.002.

 

Investigation into possible anaerobic communities near Gale crater, an experimental Bayesian approach
Dylan Verburg (TU Delft), supervisor: Ralph Lindeboom

The 14th of July 2013, a methane peak was observed in the Gale crater. This methane peak has been investigated in non-biological context before. This study applies exoplanet research strategies and knowledge about biological methane production on Earth to investigate the complementary biological context. Thermodynamic calculations show methanogenesis and sulphate reduction to be viable catabolic reactions under Mars temperatures and concentrations. Experiments into methane and hydrogen sulfide gas, as well as biomass growth, were conducted on organisms gathered from Boom clay porewater. These experiments show that methane and hydrogen sulfide gas production are sparsely affected by the introduction of modified Phylosilicate Martian Regolith Analog (P-MRA) and Martian Atmosphere Analog (MAA). Biomass growth is not consistent between the tests. Comparison with the ADM1 kinetic model shows that only methane gas can be compared. Biomass and sulphur gas production is inconsistent between experiments and the kinetic model. Using the modified ADM1 model, a Monte Carlo (MC) approach was used to assess the correlation between the observed methane peak and the kinetic model results. Based on this, 78% of the simulations showed a significant correlation. Using Bayesian inference, the posterior probability of the methane peak being biological in origin is higher than the prior probability of an anaerobic community being active around the Gale crater. This goes for all prior probabilities of an active anaerobic community existing, and all prior probabilities of the methane being produced abiotically below 0.78.

 

Impact-induced Formation of Prebiotic Molecules on Terrestrial Planets
Andrea Zorzi (Stanford University), Laura K. Schaefer

New chemical species can form from reactions induced by shock-heating upon formation of an impact vapor plume and its interaction with the background atmosphere of a rocky planet. Previous studies have assumed chemical equilibrium in computing the abundance of chemical species: such a simplified model can underestimate those concentrations by a factor of 10 in high temperature shock conditions. A more accurate description of the plume/atmosphere interaction demands a coupled hydrodynamics and kinetics calculation. We present a new model extending the work of Ishimaru et al. (2010) by considering an atmosphere on the target planet. We assess the production of prebiotic molecules (HCN, CH4, NH3) for different impact scenarios, varying kinetic energy of the impactor, atmospheric surface density and composition. We find that prebiotic species are produced on Earth-like planets with a N2-CH4 atmosphere, with increasing abundance when: i) the atmospheric surface density increases; ii) the impact energy decreases; iii) the amount of methane in the pre-existing atmosphere increases. The presence of oxygen in today's inner solar system planets prevents the production of HCN. On Titan, impacts can constitute an additional sink for methane. Our findings provide necessary but not sufficient conditions for prebiotic chemistry to start, to assess the astrobiological potential of impacts on terrestrial worlds.

 

Atmospheres

 

Modelling Jupiter's Atmosphere; More Simplistic Models for More Applicable Results
Charlotte Alexander (University of Oxford), Patrick Irwin

There are many current cloud models of Jupiter, typically involving several cloud and haze layers, that are able to successfully reproduce visible observations of the planet. However it is often difficult to differentiate between these models due to the high amount of degeneracy between the parameters in the models. This leads to several models being able to reproduce observations equally successfully, despite different values for model parameters, leading to an inability to conclude on the most realistic atmospheric set up for Jupiter's clouds. By introducing a new method [1], utilising two viewing angles, it helps to break some of the degeneracy of the problem. We were able to show that some previous models such as [2], which are highly successful at reproducing one viewing angle observations, are unable to fit to a high viewing angle simultaneously to a nadir observation, as successfully as a single observation. Therefore utilising the dual viewing angle technique allows us to derive a model which can reduce the degeneracy between the parameters, due to pre-determining some parameters before a retrieval. Hence we aim to find a model which is able to fit the two angle observations comparatively, or better, than the models derived for single viewing angles. A uniform main cloud pressure for all latitudes in the study (50°S-50°N) has been inferred using the techniques outlined in [3]. From this point fitting for other parameters including the refractive imaginary index, can be done using the Non-Linear Optimal Estimator for Multivariate Spectral Analysis (NEMESIS) algorithm [4], in order to build a cloud model. Expansion of the above technique to specific features such as the Great Red Spot will also be done to see how the cloud structure varies between the GRS and other regions being parameterised. Hence cloud structure can be determined globally whilst eliminating some of the degeneracy which in the past had lead to a difficultly discerning the most realistic cloud model for Jupiter. These models can then be tested using the highly detailed observations of Jupiter that have been taken by JWST in its first year of operation, particular the GRS, adding to the validation of the model that is determined by application of this technique. Therefore this work will detail the steps undertaken and the models retrieved in order to reduce some of the degeneracy in the atmospheric modelling of Jupiter at no expense to the atmospheric fit retrieved. [1] Pérez-Hoyos, et al., (2020), Icarus, 352:114031 [2] Braude, et al., (2020), Icarus, 338:113589 [3] Irwin, et al., (2008), JQSRT, 109:1136-1150 [4] Irwin, et al., (2022), JGR:Planets, 127, e2022JE007189

 

The evolution of atmospheric escape as seen through the helium 1083nm triplet
Andrew Allan (Leiden Observatory, Leiden University), Aline Vidotto, Carolina Villarreal D'Angelo, Leonardo dos Santos

Atmospheric escape has traditionally been observed in Lyman-alpha transits, but more recently detections using the metastable helium triplet 1083nm line were obtained. Given its ability to be observed from the ground, the 1083nm helium line offers more possibilities for studying atmospheric escape. One issue however is that the formation of this line is strongly dependent on the specific high-energy flux received by the planet. Previous studies have shown that the extreme-UV band both drives atmospheric escape and populates the triplet state, whereas lower energy mid-UV radiation depopulates the triplet state through photoionisations. The goal of our own work is to understand how the observability of escaping helium evolves as the planet ages. For that, we couple our one-dimensional hydrodynamic non-isothermal model of atmospheric escape with a ray tracing technique in order to predict the physical nature and observability of escaping helium as the planet ages. In our models, we consider the evolution of the stellar high-energy radiation and the evolution of the planet gravitational potential, both of which contribute to a decline in the rate of atmospheric escape. We show also how the assumed fraction of helium to hydrogen as well as often neglected helium heating and cooling processes affect both the escape hydrodynamics and the helium observations.

 

Modelling Atmospheric Erosion for Terrestrial Planets in the Solar System
Maria Luisa Alonso Tagle (BIRA-IASB), M. L. Alonso Tagle, R. Maggiolo, H. Gunell, J. De Keyser, G. Cessateur, G. Lapenta, V. Pierrard, A. C. Vandaele

Since the Great Oxidation Event, the oxygen escape rate on Earth has changed over time mainly due to solar evolution. Two solar agents drive the Earth's atmospheric erosion rate: the solar wind and the EUV radiation. The first one affects the non-thermal processes by changing the plasma conditions, and the second one affects both types of processes: by increasing the atmospheric temperature, and by modifying the ion production rate. Hence EUV radiation affects atmospheric parameters, such as the exobase distance and neutral density, which influence the escape rate. In this work, we describe a model that uses in-situ measurements and physical considerations to estimate the effect of solar evolution on the atmospheric loss rate. Physical assumptions are made to describe the contribution of the solar wind pressure on each erosion mechanism. The main objective is to reproduce earlier solar conditions to constrain oxygen loss over geological time scales. Seven different mechanisms are studied, to determine the fundamental factors that have a significant impact on the oxygen escape rate in the past Earth. We discuss the effects of the exospheric parameters and solar wind drivers on the oxygen erosion rate. We examine their relevance for total oxygen loss and their influence on the stability of our atmosphere.

 

The LIFE space mission: characterizing atmospheres of terrestrial exoplanets and searching for habitable worlds and biosignatures
Daniel Angerhausen (ETH Zürich), and the LIFE Initiative

In this poster we will give a general introduction and overview to the LIFE (Large Interferometer for Exoplanets) mission concept. We will summarize the status and prospects of LIFE in context of the ESA Voyage 2050 Senior Committee Report, present it's science objectives and show ways to contribute to the initiatives efforts.

 

HCN photochemistry in HD 209458 b and WASP-76 b
Robin Baeyens (Anton Pannekoek Institute for Astronomy, University of Amsterdam)

Photochemistry is an important phenomenon that shapes the atmospheric composition of hot Jupiters. This has been illustrated plain and clear through the detection of SO2, a photochemically produced molecule in the atmosphere of WASP-39 b. In addition, several high-resolution spectroscopy detections of HCN have been reported, which could be linked to the elemental C/O ratio of the planet. However, given the known photochemical origin of HCN, this interpretation requires accurate photochemical modelling. Here, I present recent results of pseudo-2D photochemical kinetics models of HD 209458 b and WASP-76 b, providing predictions of the HCN abundance, as well as implications carried by the recent HCN detections.

 

Investigating Thermal Contrasts Between Jupiter's Belts, Zones, and Polar Regions with VLT/VISIR
Deborah Bardet (School of Physics and Astronomy, University of Leicester, Leicester, UK), Padraig T. Donnelly, Leigh N. Fletcher, Arrate Antuñano, Michael T. Roman, Glenn S. Orton, Sandrine Guerlet, Henrik Melin, Jake Harkett

Concerning the Jovian polar regions, the analysis of VISIR imaging shows a large region of mid-infrared cooling poleward ~67°S, co-located with the reflective aerosols observed in methane-band imaging by JunoCam, suggesting that they play a key role in the radiative cooling at the poles, and that this cooling extends from the upper troposphere into the stratosphere. These VISIR observations also reveal thermal contrasts across polar features, such as numerous cyclonic and anticyclonic vortices, as well as evidence of high-altitude heating by auroral precipitation. Comparison of zonal mean thermal properties and high-resolution visible imaging from Juno allows us to study the variability of atmospheric properties as a function of altitude and jet boundaries, particularly in the cold southern polar vortex. To investigate the radiative processes and influence of auroral precipitation on the southern cold vortex, a radiative-convective model tailored for Jupiter's atmosphere (Guerlet et al., 2020), with an updated polar aerosol distribution from Juno mission results, will be used to determine the aerosol distribution needed to reproduce the thermal structure of the cold polar vortex of Jupiter.

 

Water-Hydrogen Demixing and the Atmospheric Water Abundance of Uranus and Neptune
Marina Cano Amoros (DLR-German Aerospace Center), Nadine Nettelmann, Nicola Tosi

Understanding the atmospheric water abundance of solar and extrasolar giant planets can reveal important insights into their internal structures. Recent water abundance measurements from JUNO at Jupiter showed that the atmosphere is less enriched in water than what the gravity data implies for the deep interior, yielding an inhomogeneous and H-He dominated interior [1]. For the ice-rich outer planets Uranus and Neptune, interior models constrained by the observed gravitational harmonics J2 and J4 also indicate that their interiors are composed of a H/He-rich envelope but atop an ice-rock-rich interior. The transition occurs at pressures of a few (tens) of GPa. However, formation theories can explain such a highly inhomogeneous composition profile [2] only if specific conditions are assumed [3]. Alternatively, the phase separation of the two major constituents water and molecular hydrogen has been proposed as an explanation for their current structures [4]. In this scenario, water would rain out to deeper levels and deplete the atmosphere in water over time. Here, we follow up on the possibility of demixing in the H-He-H2O system. We employ a water-hydrogen phase diagram constrained by experimental data up to 3 GPa [4]. We show that demixing can occur over a wide range of assumed initial bulk water abundances and that this process may have started already billions of years ago, with higher ice abundances leading to colder interiors and earlier onsets of demixing. Our models suggest similar atmospheric water abundances for both planets. However, a major uncertainty arises from the poorly known phase diagram at pressures beyond 3 GPa. To account for uncertainties we adopt a Monte Carlo approach implemented within the TATOOINE code for exoplanet structure modelling [5]. Acknowledgements: MC and NT acknowledge support from the Research Unit 2440/2 funded by the DFG (Deutsche Forschungsgemeinschaft). NN acknowledges support through NASA's Juno Participating Scientist Program under grant 80NSSC19K1286. References: [1] Miguel Y., Bazot M., Guillot T. et al., AA 662:A18 (2022) [2] Helled R., Nettelmann N., Guillot T., SSRv 216:38 (2020) [3] Frelikh R. and Murray-Clay R.A., AJ 154:98 (2017) [4] Bailey E. and Stevenson D.S., PSJ 2:64 (2021) [5] Baumeister P., Padovan S., Tosi N. et al., ApJ 889:42 (2020)

 

Quantifying trace gases in the lower atmosphere of Titan using Huygens GCMS
Koyena Das (LATMOS-CNRS), Thomas Gautier, Joseph Serigano, Cyril Szopa, Sarah M. Hörst, Maélie Coutelier, Sandrine Vinatier, Melissa G. Trainer

In Titan, the two major gases nitrogen (N2) and methane (CH4) are ionized and/or photolyzed at high altitudes by the sunlight and the energetic particles from Saturn's magnetosphere, resulting in rich atmospheric chemistry and a wide variety of carbon and nitrogen-bearing atmospheric compounds. In the present work, we focus on studying the vertical profiles of trace species in the lower atmosphere to obtain a better insight into the atmospheric processes taking place on Titan. To do so, we reanalyzed the data from the Gas Chromatograph Mass Spectrometer (GCMS) on the Huygens probe which executed its mission on 14th January 2005. The GCMS instrument sampled for nearly three and a half hours from a height of 146 km. It recorded data for two and a half hours in the atmosphere of Titan, then landed on the surface and kept on recording for another hour, after which the signal was lost. We analyzed the measurements made by direct sampling of the atmosphere. These mass spectra obtained at different altitudes and pressure levels have been recalibrated to account for deadtime and saturation corrections to the measurements and considered ion cross-section and transfer cross-section measurements from Cassini-Ion and Neutral Mass Spectrometer calibrations. We then analyzed the corrected mass spectra using Monte-Carlo deconvolution simulations. The simulations allow us to vary the peak intensities of fragmentation patterns of known species, which usually bears uncertainties on this kind of data, and then use a least-square fitting to deconvolve the mixed signals. This is the first time mixing ratios of high-altitude trace gases could be quantified using this GCMS data. Currently, we are working with 10 species and developing their vertical profiles in the atmosphere. In the future, we plan to extend this study to develop a sub-surface model of Titan which will help us understand the outgassing of methane that was observed by the probe upon its touchdown on the surface.

 

Looking above the cloud deck of GJ 3470b
Spandan Dash (University of Warwick), Dr. Matteo Brogi, Dr. Siddharth Gandhi

Characterisation of cooler atmospheres of super-Earths and Neptune sized objects at low-resolution is often thwarted by the presence of clouds, hazes and aerosols which effectively flatten the transmission spectra. High-Resolution Spectroscopy (HRS) presents an opportunity to overcome this limitation by having the ability to detect molecular species whose spectral line cores extend above the level of clouds in these atmospheres. We analyse High-Resolution observations of the warm Neptune GJ 3470b taken over two transits using CARMENES (R ~ 80400) and look at the possibility of H2O signatures in these transits. We find that our custom pipeline can provide an unambiguous detection of H2O using two transits when they have an injected signal equivalent to the level of what has been observed using HST WFC3 + Spitzer at low resolution. Using a Bayesian retrieval tool on the two observed transits to put simultaneous constraints on the abundance of H2O and the cloud top-deck pressure selects for low abundance and deep cloud deck (clear atmosphere) models, which is in slight dissonance with published results from low resolution.

 

Applications of Approximate Bayesian Computation (ABC) within Exoplanet Atmospheric Studies
Jack Davey (University College London (UCL)), Ingo Waldmann, Ahmed Al-Refaie

While Approximate Bayesian Computation (ABC) and other likelihood free (LF) methods for Bayesian inference have been adopted in many areas of scientific research including cosmology, they have seen limited application in exoplanetary science. Cosmologists have been dealing with the problem of intractable likelihoods for a number of years and have implemented these techniques in order to bypass the need to define a likelihood function. With the launch and first observations of the James Webb Space Telescope (JWST), there is a strong expectation that assumptions in the likelihood could bias results of atmospheric retrievals on exoplanet transmission spectra so the need for LF methods is evident now more than ever. Here, we implement ABC with the atmospheric retrieval code TauREx3 (using the PyMC library) with the aims of revealing and mitigating the effects of non-gaussianity in spectral data sets. To this end we will study effects due to non-gaussian noise in simulated data sets of hot Jupiter spectra. This will allow us to identify any biases on specific parameters and we will then go on to perform a reanalysis of Hubble and JWST early release science observations to identify any non-gaussian bias in retrievals performed with these data.

 

Perturbation of exoplanetary spectra in cool stars transit spectroscopy
Pierre Drossart (Institut d'Astrophysique de Paris / CNRS, Sorbonne Université), Emilie Panek (IAP), Andrea Chiavassa (OCA), Jean-Philippe Beaulieu (IAP), Matteo Brogi (U. Warwick)

The interference between the molecular lines in cool stars (K or M spectral types) and a transiting planet observed by transit spectroscopy can produce important biases in the molecular retrieval of the planetary composition, in particular for CO or H2O molecules which are present in K or M stars (Drossart et al. COSPAR 2022). Here we present a deeper analysis of the effect on realistic model of star WASP 43 limb profile, including Doppler shift variation during transit and stellar limb darkening (Chiavassa & Brogi, 2019). This work constitutes a template for future stellar corrections to be taken into account in the frame of JWST and Ariel retrievals of transiting planet spectroscopy in the case of K or M star presenting molecular absorptions coincident with the planetary absorptions.

 

Laboratory measurements of ferric chloride as a major contributor to the anomalous UV absorption in the Venusian atmosphere
Joanna Egan (University of Leeds), Alexander James, James Manners, Daniel Marsh, John Plane

In-situ probe measurements and remote sensing have revealed that Venus has a highly organised cloud system. Comparisons between models of the expected spectrum and observations reveal unexplained absorption in the near-UV to blue region of the spectrum. While many candidates for this “unknown absorber” have been proposed over the years, none have been conclusively demonstrated to match the physical and optical behaviour observed (Pérez-Hoyos et al., 2018, JGR Planets, 123). One such candidate is ferric chloride (Krasnopolsky, 2017, Icarus, 286; Zasova et al., 1981, ASR, 1). Attempts to reliably determine its suitability have been hampered by the scarcity of representative spectra available. The FeCl3 absorbance spectrum generally used in the literature is measured in ethyl acetate (Aoshima et al., 2013, Polymer Chemistry, 4), and therefore may not be representative of the absorption produced by ferric chloride in the Venusian clouds. We present absorption spectra of ferric chloride in sulphuric acid, measured using UV-Vis spectrometry. This change of solvent produces an environment more closely aligned to that on Venus, where ferric chloride, if present, may exist as an impurity in the micron-sized sulphuric acid cloud droplets (Petrova, 2018, Icarus, 306). We also utilise 1D multiple scattering radiative transfer modelling to estimate the concentration of ferric chloride required to explain the observed absorbance. The unknown absorption was first observed close to 100 years ago, yet the mystery of its cause remains unsolved. More representative spectra of ferric chloride and a greater understanding of its behaviour in the atmosphere of Venus are critical to advancing the identification of the unknown absorber. As the absorber is located towards the top of the clouds and absorbs in the near-UV to blue region, it is responsible for large amounts of absorption of incident sunlight, and therefore has a significant impact on the Venusian energy budget. Accurate atmospheric modelling of the planet therefore requires an understanding of the absorber which can only be achieved once it has been conclusively identified.

 

Surprising Decrease in the Martian He Bulge during PEDE-2018 and Changes in Upper Atmospheric Circulation
Meredith Elrod (University of Maryland College Park / NASA GSFC), Stephen Bougher, Kali Roeten

Using the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere Volatile and Evolution spacecraft (MAVEN) we analyzed data from Mars Year (MY) 32, 34, and 35 to examine the He bulge during the northern winter solstice (Ls ~180-240) specifically focusing on the effects from the planet encircling dust event (PEDE-2018). He collects on the dawn/nightside winter polar hemisphere of the terrestrial planets (Earth, Mars, and Venus). The seasonal migration of the Martian He bulge has been observed and modeled (Elrod et al., 2017, Gupta et al., 2021). The MAVEN orbit precesses around Mars allowing for a variety of latitude and local time observations throughout the Martian year. MY32, 34 and 35 had the best possible opportunities to observe the He bulge during northern winter (Ls ~180-240). NGIMS observations during MY 32 and MY 35 revealed a He bulge on the nightside to dawn in alignment with modeling and previous publications. However, in MY 34, during the PEDE, the He bulge was not present indicating the PEDE directly impacted upper atmospheric circulation. Updates in modeling indicate changes in circulation and winds can cause He to shift further north and dawn-ward than MAVEN was able to observe. The temperature increases in the thermosphere on the nightside during the dust storm along with changes in gravity waves and eddy diffusion occurring during this event could account for this circulation change.

 

Ground-based, high-resolution spectroscopy of exoplanet WASP-18b: Atmospheric composition and dynamics
Vanessa Emeka-Okafor (University of Warwick)

We present high-resolution dayside thermal emission observations of the ultra-hot Jupiter WASP-18b using IGRINS on Gemini South. Using standard algorithms, we remove the stellar and telluric signatures and extract the planet signal via cross-correlation with model spectra. Our results demonstrate that ground-based, high-resolution spectroscopy at infrared wavelengths can provide meaningful constraints on the compositions and climate of highly irradiated planets. We detect the atmosphere of WASP-18b at a signal-to-noise ratio (SNR) of 5.9 using a full chemistry model, measure H2O (SNR=3.3), CO (SNR=4.0), and OH (SNR=4.8) individually and confirm previous claims of a thermal inversion layer. We use a Bayesian inference framework to retrieve abundance, temperature, and velocity information. For this ultra-hot Jupiter, thermal dissociation processes likely play an important role. Retrieving abundances constant with altitude and allowing the temperature-pressure profile to freely adjust results in a moderately super-stellar carbon-to-oxygen ratio (C/O=0.75^{+0.14}{-0.17}) and metallicity ([M/H]=1.03^{+0.65}{-1.01}). Accounting for undetectable oxygen produced by thermal dissociation leads to C/O=0.45^{+0.08}{-0.10} and [M/H]=1.17^{+0.66}{-1.01}. A retrieval that assumes radiative-convective-thermochemical-equilibrium and naturally accounts for thermal dissociation constrains C/O<0.34 (2-sigma) and [M/H]=0.48^{+0.33}_{-0.29}, in line with the chemistry of the parent star. Looking at the velocity information, we see a tantalizing signature of different Doppler shifts at the level of a few km/s for different molecules, which might probe dynamics as a function of altitude and location on the planet disk. Our work also elucidates potential pitfalls with commonly employed retrieval assumptions when applied to UHJ spectra. Overall, our study highlights the potential of ground-based, high-resolution spectroscopy to uncover the atmospheric composition and dynamics of highly irradiated exoplanets, shedding light on their formation and evolution.

 

Temperate exoplanets observable with Ariel : an update with new targets from TESS
Therese Encrenaz (Paris Observatory), A. Coustenis, B. Edwards, K. Molaverdikhani, M. Ollivier, G. Tinetti

In 2018 and 2022, we have published an analysis of the observability of temperate planets (with an equilibrium temperature of about 300-550 K) with ARIEL [1, 2]. This presentation is an update of this analysis which uses new targets identified in particular from the TESS database [3] and investigates their observability with ARIEL. Using the parameters of these new targets, and an atmospheric mean molecular weight of 2.3 g/mol (corresponding to a hydrogen-rich atmosphere), and using the ArielRad code [4], we give an estimate of the number of transits (T2) needed for these objects to be observed in the Tier 2 mode of the space mission, i. e. with a S/N @ 7 . The Tier 2 spectroscopic mode (R @ 10 for 1.1 µ­m < l < 1.95 µ­m, R = 50 for 1.95 µ­m < l < 3.9 µ­­m, R @ 15 for 3.9 µm < l <7.8 µm) will allow us to infer constrains about the atmospheric composition of these targets. Preliminary results of this study are given below: 1) Using the candidate list of Edwards and Tinetti (2022) [3], we find 22 targets with T2 < 35, observable during the lifetime of ARIEL. 2) 7 among these targets, with a mass above 5 terrestrial masses, are presumably hydrogen-rich planets and should be observable with Ariel in the Tier 2 mode. In particular, the big Neptune TOI-3884 b, with T2 = 1, is expected to be observable also in the Tier 3 mode. 3) 8 other targets, with a mass between 1.5 and 5 terrestrial masses, will be observable in the Tier 2 mode if they have a hydrogen-rich atmosphere. The Ariel observation will thus allow us to determine whether they are sub-Neptunes or super-Earths. A promising case is LC 98-59 c and d for which the value of T2 is low (T2 = 7 and 6 respectively). 4) The 7 remaining candidates are exo-Earths, mostly from the TRAPPIST-1 system. Because their atmospheric mean molecular weight is expected to be as high as 18 g/mol (in the case of a H2O-rich atmosphere) or even more (in case of a CO/N2/CO2-rich atmosphere), they are not expected to be observable with Ariel in the Tier 2 mode. In the future, we plan to re-evaluate the observability of the candidates using different values of the atmospheric mean molecular weight. For the most favorable cases, we plan to calculate their synthetic spectra for different atmospheric compositions, considering also the possible effect of clouds. References : [1] Encrenaz et al., Exp. Astr. 46, 31 (2018) [2] Encrenaz et al., Exp. Astr. 53, 375 (2022). [3] Edwards, B. and Tinetti, G. Astron. J., 164, id.15, 25 pp. (2022) [4] Mugnai, L. V. et al. 2021b, Astron. J, 161, 284 (2021)

 

The atmosphere of ultra-hot Neptune LTT 9779 b survived thanks to an unusually slow spinning and X-ray faint star
Jorge Fernandez (University of Warwick), Peter Wheatley, George King

I present XMM-Newton observations of the sun-like star LTT 9779 together with a study of the X-ray evaporation of its transiting planet, LTT 9779 b, the first ultra-hot Neptune in the middle of the Neptune desert. The presence of LTT 9779 b so close to its star is puzzling, as the intense XUV flux it receives from its star should have stripped it of its H/He-rich atmosphere. I find that only an X-ray faint host star is able to explain both our observations as well as the survival of its atmosphere under photoevaporation. This is consistent with both an unusually slow rotation of the star for its age, and a low measured X-ray flux. LTT 9779 b is a super-Neptune (4.7 Earth radii, 28 Earth masses) that is consistent with the presence of a H/He envelope that constitutes 8% of its mass. The planet, with an age of 2 Gyr, orbits its solar-mass host star every 19 hours. This planet lies in the Neptune desert, a region of the planet radius - orbital period parameter space with very few short-period Neptune-sized planets. These planets are thought to undergo substantial evaporation due to X-ray and extreme ultraviolet radiation (together, XUV) from their host stars which heats up the upper atmosphere, driving a hydrodynamic wind that can completely strip them of their volatile-rich envelopes down to a barren rocky core. LTT 9779 b is truly unique: the only planet with an orbital period of less than a day with both measured mass and radius that maintains a significant atmosphere. In order to find feasible evaporation pasts that can explain its current state, I simulated the XUV history of its host star by modelling its spin period evolution, as the two quantities are linked through the rotation-activity relation, where faster rotators produce higher X-ray fluxes. I confirm that the XUV history expected for a solar-mass star should have already stripped LTT 9779 b of its envelope, ruling out this scenario. I then modelled a low-level XUV history that matches the measured upper limits for both its spin period and its X-ray luminosity, which I estimated using XMM-Newton measurements. I thus find that the planet's envelope can survive through 2 Gyr of irradiation under these conditions, starting out as a 6.5 Earth radii planet that has evolved to its current state through photoevaporation.

 

The Solar System planets as testing ground for exoplanets: a contribution from the Ariel Consortium Working Groups
Gabriella Gilli (Instituto de Astrofísica de Andalucia (IAA/CSIC)), G. Gilli, P. Machado, P. Drossart, T. Encrenaz, M. Rengel, D. Quirino, C. Gapp, M. Lopez-Puertas, E. Marcq, K. Molaverdikhani, J. Leconte, S. Robert, F. Oliva, A. Piccialli, A. Sanchez-Lopez, M. Lefevre, A. Spiga, P. Wolkenberg, A. Coustenis, A. Migliorini, L. Lara, F. Brasil, J. Dias, J. Silva, D. Turrini, A. C. Vandaele

The adopted ESA M4 mission Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is scheduled for launch in 2029. During its 4-year nominal mission, the space telescope aims to study 1) what exoplanets are made of; 2) how they formed and 3) how they evolve, by observing a diverse sample of about 1000 planets simultaneously in the visible and infrared wavelengths [1]. Within the ARIEL Mission Consortium, several Science Working Groups (WG) were formed in 2019 to help prepare the RedBook, defining the science cases, and to contribute to address the 3 fundamental questions above. Among those WGs, "Synergies between Solar System planets and exoplanets" was set-up to foster collaboration between the scientific community working on Solar System (SS) Planets atmospheres and the new growing community of the Ariel Science Team. The planetary exploration and research with a focus on comparative planetology has played an important role in our understanding of climate on Earth. Although optimal ARIEL targets are hot and warm giant planets close to their host star, a long-term scientific objective is characterising the whole range of exoplanets, including potentially habitable ones. We show an overview of on-going studies and future projects foreseen by WG members, mostly focused on using our Solar System planets as proxies to develop and test tools to support ARIEL science cases. For instance:

• Jupiter is taken as a benchmark for gas Giant planets to study physico-chemical processes that could help to better understand hot-Jupiters and interpret observations of a whole category of exoplanets. The measured composition and isotope ratios can help to test planet formation mechanisms in other systems [2,3]. We also take into account recent efforts that are being carried out with JWST observations, and future efforts with JUICE. In addition, Uranus and Neptune are considered as a subcategory of ice giants planets that are more representative of colder objects.
• To search for new Ariel targets, the TESS database has been used to investigate the observability of "temperate" exoplanets (with temperatures ranging between 350 K and 500 K) [4].
• General Circulation Models (GCMs) developed for Solar System planets have been applied to specific cases of known rocky exoplanets (e.g., Trappist-1c, LP 890-9c), under the hypothesis that their atmosphere evolved into a modern Venus. As a first step, our goal is to study the impact of atmospheric dynamics on the phase curve, as if they were observed by JWST [5, 6]. 
• GCMs and convection-resolving models will be also used to study the terrestrial exoplanets cloud characteristics (spatial coverage, altitude range, temporal variability) for different surface pressure and atmospheric dynamical regime to help retrievals and analyse the data through the observation of phase curves of exoplanets [7].
• We also plan to use Earth resolved spectra to craft observations of Earth-like planets with different percentages of surface/cloud endmembers in the field of view. By integrating these observations into a single pixel, it is possible to derive the percentages needed to identify each endmember in the resulting spectrum. Even if not directly related to the science that ARIEL will be doing, such an analysis can provide a good framework to understand what we expect to see in these objects [8,9].
• We retrieved a transmission spectrum of the atmosphere of Venus, using high resolution observations performed with FIRS instrument at Dunn telescope, during the solar transit in June 2012, the last one before 2117. This event was a unique opportunity to assess the feasibility of the atmospheric characterisation of Earth-size exoplanets near the habitable zone with the transmission spectroscopy technique and provide an invaluable proxy for the atmosphere of such a planet. Our aim is to produce a valuable template of a transit of Venus-like planets around Sun-like stars in a unique calibration opportunity.

References: [1] Tinetti et al. RedBook, [2] Gapp, C. (2021). Master's thesis: 'Characterization of Jupiter's atmosphere using far infrared spectra measured with PACS onboard the Herschel Space Observatory'. Georg-August-Universitaet Goettingen, Germany [3] Gapp, Rengel, Hartogh et al. in preparation [4] Encrenaz et al. 2021, Experimental Astronomy [5] Quirino et al. MNRAS, under review [6] Quirino, D (2022). Master's Thesis: 'Modelling Venus-like exoplanetary atmospheres with a GCM: planetary parameters impact on the large-scale circulation and observational prospects'. Faculty of Sciences, University of Lisbon, Portugal, [7] Turbet et al. 2016A&A...596A.112T, [8] Oliva et al. EPSC Abstracts. Vol. 11, EPSC2017-531, 2017, [9] Oliva et al. EGU 2017, Geophysical Research Abstracts Vol. 19, EGU2017-17016, 2017

 

Current challenges in Giant planet atmospheric modelling
Sandrine Guerlet (Laboratoire de Meteorologie Dynamique / CNRS), Aymeric Spiga, Deborah Bardet, Gwenaël Milcareck, Alexandre Boissinot, Ehouarn Millour

The atmospheres of the four giant planets of the Solar System present a rich and varied meteorological activity. The dominant flow, well documented in their troposphere thanks to cloud tracking, consists of jet streams encircling these planets alternatively (depending on the latitude) from east to west or from west to east. The number and speed of these jets vary greatly depending on the planets, reaching 27 jets for Jupiter and only three for Uranus and Neptune, and reaching +400 m/s at the equator on Saturn and -400 m/s at the equator on Neptune. Various waves, cyclones, anticyclones, giant storms and other polar vortices, imaged from the ground or from space (Juno, Cassini, HST, ...), complete this picture. Above the troposphere, all have a stratosphere, a region where the temperature increases with altitude. In this region, anomalies observed in the temperature and composition fields (mainly by infrared spectroscopy) indicate the presence of seasonal circulation cells on Saturn as well as periodic oscillations in temperature and zonal wind at the equator of Jupiter and Saturn. These observations have motivated the development of general circulation models adaptable to each giant planet, in order to better understand the organization of the flow in these fluid planets and the processes underlying the observed phenomena. Our model, named DYNAMICO-PCM, solves the Navier-Stokes equations on the rotating sphere on an icosahedral grid with a fairly high spatial resolution (typically 1°). The model extends from the troposphere (a few bars) to the stratosphere (a few microbars) and takes into account radiative and seasonal exchanges, including the effect ring shadowing on Saturn and radiative forcing by polar hazes (related to auroral/ion chemistry) on Jupiter. We will present a review of the atmospheric modeling work recently carried out in the LMD planetary science team. Among the main results obtained, let us quote the reproduction of the equatorial oscillation of Saturn and its seasonal circulation cells, forced by the activity of planetary waves; and the forcing of realistic jet streams in the Jupiter model thanks to the addition of a sub-grid scale parametrization of convective plumes. Challenges that remain to be addressed as well as comparisons to observations will be presented.

 

Machine learning as a tool to determine exoplanet properties
Thomas Hajnik (University of Vienna / Department of Astrophysics), Thomas Hajnik, Andreas Schanz, Sudeshna Boro Saika

Characterization of exoplanetary atmospheres and interiors requires information on planetary properties such as mass, radius, and density. However, precise measurements of these fundamental properties are not always possible, as a result of which the masses and radii of these planets are often unknown. We propose a data driven machine learning method to estimate missing exoplanet properties by applying clustering algorithms to a subset of the currently known exoplanet populations, containing approximately 4000 exoplanets. We applied the Uniform Manifold Approximation Projection (UMAP, McInnes et al., 2018) algorithm, together with a range of clustering techniques, such as Gaussian Mixture Models, K-means and HDBSCAN, to a custom data set, created by merging the NASA exoplanet archive and the exoplanet.eu catalogue. This enables us to create the most complete parameter set, that current observations allow. We show that a combination of different clustering algorithms and trained UMAP models is able to infer estimates on planetary radii and masses, when provided with a large enough training sample. Based on this method, we can provide estimates for radii and masses of Hot Jupiters. Our results deviate from ground truth by 0.06 Jupiter radii and 0.23 Jupiter masses on average. This is achieved for a test data set containing three host star properties (mass, radius, effective temperature) and only the orbital period of the planet. The results show that data-driven methods are a promising approach for parameter estimation in exoplanets, which can be very useful in the target characterization of upcoming missions such as PLATO and Ariel.

 

Improving Exoplanet Atmospheric Retrievals with a Learning-Based Model for Pressure-Temperature Profiles
Björn S. Konrad (ETH Zürich), T. D. Gebhard, D. Angerhausen, E. Alei, S. P. Quanz, and B. Schölkopf

Atmospheric retrievals are commonly used to infer exoplanet properties (e.g., the chemical composition of the atmosphere) from an observed spectrum. A retrieval framework requires a forward model (calculates the spectrum corresponding to a set of model parameters) and a Bayesian inference scheme (samples the space of model parameters in search of the best combination). One important component of the forward model is the pressure-temperature (PT) profile, which describes the thermal structure of the atmosphere. Retrievals typically employ parametric functions to describe the atmospheric PT structure (e.g., polynomials in Konrad et al. 2022). While being versatile, such parametric forward models are not physical. Thus, we have no guarantee that the retrieved PT structure describes a physically possible atmospheric state. Furthermore, parametric forward models require large parameter numbers (more than 4), which slows down the atmospheric retrieval routine. We employ a new Machine Learning (ML) approach to parameterize the PT structure of exoplanet atmospheres in retrieval studies. This new approach requires fewer parameters (only two) and is trained on physically accurate PT profiles. We train our ML model on the PyAtmos data set (Bell at al. 2018, Chopra et al. 2018), which consists of more than 100000 physically and chemically self-consistent PT profiles of Earth-like planets around a solar-type star, which were calculated with Atmos (a one-dimensional coupled photochemistry-climate model; Arney et al. 2016, Meadows et al. 2018). To prove the applicability of the ML PT Model, we run atmospheric retrievals on a low resolution (R=50) MIR thermal emission spectrum of an Earth-twin exoplanet. We find that employing our ML PT model speeds up the retrieval significantly over the baseline retrieval with a polynomial PT model (by roughly 50%). The retrieved values for most planetary and atmospheric parameters are comparable. However, the retrieval that employs the ML PT model provides better estimates for the atmospheric PT structure than the polynomial baseline. These retrieval runs show the potential of ML-base PT models for atmospheric retrievals. Such models provide a physically accurate description of atmospheric PT profiles while requiring less parameters than the commonly used parametric PT models. References: Arney, G., Domagal-Goldman, S. D., Meadows, V. S., et al. 2016, Astrobiology, 16, 873 Bell, A., Chopra, A., Fawcett, W., et al. 2018, in 5th Workshop on Challenges in Machine Learning (NeurIPS) Chopra, A. et al. 2018, About the FDL PyATMOS dataset Konrad, B. S., Alei, E., Quanz, S. P., et al. 2022, A&A, 664, A23 Meadows, V. S., Arney, G. N., Schwieterman, E. W., et al. 2018, Astrobiology, 18, 13

 

Atmospheric Retrieval of Terrestrial Solar System Planets for LIFE
Björn S. Konrad (ETH Zürich), Eleonora Alei, Daniel Angerhausen, Sascha P. Quanz, and the LIFE collaboration

Context: A long-term goal of exoplanet research is to characterize the atmospheres of a sizable sample of temperate terrestrial exoplanets. Such studies will build our knowledge about the diversity of terrestrial worlds and enable the discovery of habitable or even inhabited worlds. To achieve this goal, missions capable of measuring the spectra of temperate terrestrial exoplanets have been proposed (LUVOIR/HabEx - optical & near-infrared; Large Interferometer For Exoplanets (LIFE)[1] - mid-infrared (MIR)). The MIR thermal emission measured by LIFE provides exclusive probes to important molecules (e.g. the potential bioindicators CH4, O3). Further, the MIR observations can provide constraints on a planet’s pressure-temperature (PT) profile, radius, and surface conditions. Methods & Results: We present results from our recent atmospheric retrieval studies. We investigated a cloud-free Earth- [2] and, to our knowledge for the first time, a cloudy Venus-twin [Konrad et al., subm.] exoplanet around a sun-like star at 10 pc. We simulate the MIR planet emission spectra with petitRADTRANS (1D radiative transfer model) [3] and use LIFESim [4], to estimate the wavelength-dependent noise expected for exoplanet observations with LIFE. Our retrieval suite uses the atmospheric model petitRADTRANS and the MultiNest algorithm [5] for parameter estimation. We retrieve the planetary mass and radius, the PT profile, the surface pressure, the molecular abundances and the cloud parameters. By considering input spectra of different wavelength ranges, resolutions (R), and noise levels (S/N), we aim to determine the requirements to: 1. discriminate Earth- from Venus-like MIR spectra 2. characterize the structure and composition of atmospheres 3. detect potential biomarkers in Earth-twin 4. infer the presence of clouds in atmospheres 5. constrain cloud structure and composition in a Venus-twin We also discuss challenges in the analysis of MIR exoplanet spectra from LIFE via atmospheric retrievals and how differences in the quality of the spectra affect them. Conclusion: With these studies and an additional retrieval study for Earth at different times [6], we find first constraints for the instrument requirements for the LIFE interferometer and identify important limitations and challenges of MIR atmospheric retrieval studies for exoplanets. References: [1] Quanz, S. P., et al. 2022, A&A, 664:A21 [2] Konrad, B. S., et al. 2022, A&A, 664:A23 [3] Mollière, P., et al., 2019, A&A, 627:A67 [4] Dannert, F. A., et al. 2022, A&A, 664:A22 [5] Feroz, F., et al., 2009, MNRAS, 398(4):1601–1614 [6] Alei, E., et al. 2022, A&A, 665:A106

 

Convection inhibition in the atmosphere of Neptune and Neptune-like planets
Jeremy Leconte (LAB/CNRS), Jeremy Leconte, Aymeric Spiga, Sandrine Guerlet, Franck Selsis, Gwenaël Milcareck, Noé Clément, Ehouarn Millour

Whether it is inside or outside of the Solar System, the atmospheric structure of Neptune and Neptune like planets remains rather poorly constrained. On the observational side, JWST will soon change by observing our own ice giants, but also temperate sub-neptunes like K2-18b, thanks to their relatively large size compared to terrestrial planets. However, on the theoretical side, models of the atmospheric structure and dynamics of these atmospheres are relatively scarce. In particular, it has been proposed that water (or methane) condensation could shut down convection in planets where it is heavier than the background hydrogen rich atmosphere (like Neptune; Leconte et al. 2017). But the dynamics of this effect has never been studied in 3D and its impact of this on observations (in particular for exoplanets) has never been assessed. I will show results from a 3D cloud-resolving model that we adapted to the study of temperate hydrogen rich atmospheres. This work shows how water condensation naturally shuts down convection in these objects as has been predicted by simple linear theory. Then, we will show how the thermal and compositional structure of these atmospheres is modified. Finally, we will discuss whether convection inhibition yields an observable signature for JWST to detect. Leconte et al. 2017 - https://ui.adsabs.harvard.edu/abs/2017A%26A...598A..98L/abstract

 

New spectral windows into the escaping atmospheres of exoplanets
Dion Linssen (University of Amsterdam), Antonija Oklopčić 

Atmospheric escape is expected to have important consequences for the evolution of planets and has been suggested to create the observed radius valley and hot Neptune desert. To date, escaping exoplanet atmospheres have typically been probed with a handful of spectral lines, such as Lyman alpha, the metastable helium triplet and UV lines of metals. Inferring important characteristics such as the outflow geometry and mass-loss rate from these observations has been difficult due to differing theoretical predictions and model degeneracies. Expanding on the suite of tracers used to probe escaping atmospheres would help to mitigate these challenges. We post-process hydrodynamic outflow models with NLTE photoionization code Cloudy to predict the transit spectrum of typical gas giant planets and we find new spectral lines in the UV and optical that can potentially be used to study their upper atmospheres. By indicating the atmospheric altitude each of these lines probe, we can identify complementary lines which will allow us to better constrain the outflow properties.

 

A neural network approach to accelerate chemical kinetics codes
Amy Louca (Leiden Observatory), Julius Hendrix, Yamila Miguel

This study is focused on the implementation of neural networks to replace mathematical frameworks in the one-dimensional chemical kinetics code, VULCAN (Tsai et al. 2017; 2021). The underlying time-dependent ordinary differential equations are very time-consuming to compute when using numerical methods. The neural network in this study is designed to replace them. Our data set consists of 13291 hot-Jupiters atmospheres. Using the gravity gradient, temperature-pressure profiles, initial mixing ratios, and stellar flux as free parameters, the neural network is built to predict the mixing ratio outputs. The architecture of the network is composed of individual autoencoders for each input variable to reduce the input dimensionality, which are then used in an LSTM-like neural network to train this sequential data on. Results show that the autoencoders for the mixing ratios, stellar spectra, and pressure gradients are exceedingly successful in encoding and decoding the data. The temperature and gravity gradients are shown to be more difficult to reconstruct using autoencoders. Using the original temperature- and gravity gradients and the encoded data to predict the time-dependent output mixing ratios by training the core network has shown to be successful within errors between different chemical kinetics codes (Venot et al. 2012). In 90% of the cases, the fully trained model is able to predict the evolved mixing ratios of the species in the hot-Jupiter atmosphere simulations with errors in the range [-0.66, 0.65] orders in magnitude. Due to imbalances in the data set, the model is biased to more accurately solve for some examples than others. The fully trained model is 10^3 times faster than the VULCAN simulations while making accurate predictions.

 

YunMa: An Exoplanet Cloud Retrieval Model for Next-Generation Data
Sushuang Ma (University College London), Yuichi Ito, Ahmed F. Al-Refaie, Quentin Changeat, Billy Edwards, Giovanna Tinetti

The existence of clouds in transit spectra has been a prominent issue in exoplanetary spectroscopy. The formation of clouds can obscure the spectroscopic features from atmospheric chemistry and complicate planetary scenarios. The high-quality transit spectra offered by the next generation of facilities, such as JWST and Ariel, provide a great chance to constrain the exoplanetary cloud formation and its impact on the observation. Corresponding to the observational improvement, we present YunMa, an exoplanetary cloud model optimised for the next-generation data. Integrating YunMa into the TauREx 3 platform enables the parametric cloud microphysics retrieval function, which is a big step in exoplanetary cloud retrieval.

 

Numerical simulations of zonal jets on Uranus and Neptune by the DYNAMICO Planetary Climate Model
Gwenael Milcareck (Laboratoire de Météorologie Dynamique, CNRS, Paris, France), Sandrine Guerlet, Aymeric Spiga, Jeremy Leconte, Deborah Bardet, Franck Montmessin

Flyby of Uranus and Neptune by Voyager 2 in 1986 and 1989 have shown an intense zonal circulation and an unexpected meteorological activity. Characterized by a prograde jet at mid-latitude in each hemisphere and a retrograde jet centered on the equator, the zonal structure of the wind is similar on these two planets despite a very different seasonal radiative forcing. The retrograde jet is nevertheless more intense on Neptune where it reaches -400 m/s. In parallel with these jets, a meteorological activity in the form of waves, cyclonic and anticyclonic storms like the Great Dark Spot is also present. Understanding atmospheric circulation in gas and ice giant planets (having developed a GCM for Saturn and Jupiter as well), with comparative planetology aspects that could be relevant to the exoplanet community is one of the major current challenges in physics of planetary atmospheres. To reproduce the zonal jets as well as the strong meteorological activity on Uranus and Neptune, 1° resolution numerical simulations has been performed with a Global Climate Model (GCM) named DYNAMICO Ice Giants Planetary Climate Model. The GCM used for these studies is composed by a hydrodynamical core which solves shallow-water equations on the rotating sphere based on an icosahedral-hexagonal grid and a radiative-seasonal model tailored for ice giants. The preliminary results obtained from 10 simulated years on Uranus and Neptune highlight a similar zonal wind structure compared to observations and an important eddy activity. Spectral analysis of waves and contribution of eddies to the acceleration or deceleration of the simulated jets will be discussed.

 

Zonal winds in the Venus mesosphere from VIRTIS/VEx temperature sounding
Arianna Piccialli (Royal Belgian Institute for Space Aeronomy (BIRA-IASB)), D. Grassi, A. Migliorini, R. Politi, G. Piccioni, P. Drossart

Zonal winds in the Venus mesosphere from VIRTIS/VEx temperature sounding A. Piccialli (1), D. Grassi (2), A. Migliorini (2), R. Politi (2), G. Piccioni (2), P. Drossart (3) (1) Royal Belgian Institute for Space Aeronomy, Belgium (arianna.piccialli@aeronomie.be), (2) INAF - IAPS, Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, I-00133 Rome, Italy, (3) Institut d'astrophysique de Paris, CNRS, Sorbonne Université & LESIA, Observatoire de Paris (email: arianna.piccialli@latmos.ipsl.fr) Venus is a natural laboratory to study the atmospheric circulation on a slowly rotating planet. The dynamics of its upper atmosphere (60-120 km) is not only a combination of retrograde zonal wind found in the lower mesosphere and solar-to-antisolar winds that characterize the thermosphere, but in addition strong turbulence and a dramatic variability both on day-to-day as well as longer timescales characterizes this atmospheric layer. Moreover, several wavelike motions with different length scales were detected at these altitudes within and above the clouds and they are supposed to play an important role in the maintenance of the atmospheric circulation on Venus. The basic processes maintaining the super-rotation (an atmospheric circulation located at the clouds level and being 80 times faster than the rotation of the planet itself) and other dynamical features of Venus circulation are still poorly understood [1]. Different techniques have been used to obtain direct observations of wind at various altitudes: tracking of clouds in ultraviolet (UV) and near infrared (NIR) images give information on wind speed at cloud top (~70 km altitude) [2] and within the clouds (~61 km, ~66 km) [3], while ground-based measurements of doppler-shift in CO2 band at 10 μm [4] and in several CO (sub-)millimeter lines [5,6] sound thermospheric and upper mesospheric winds, showing strong variability. In the mesosphere, at altitudes where direct observations of wind are not possible, zonal wind fields can be derived from the vertical temperature structure using the thermal wind equation. Previous studies [7,8,9] showed that on slowly rotating planets, like Venus and Titan, the strong zonal winds at cloud top can be successfully described by an approximation of the Navier–Stokes equation, the cyclostrophic balance in which equatorward component of centrifugal force is balanced by meridional pressure gradient. We will present zonal thermal winds derived by applying the cyclostrophic balance from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) temperature retrievals. VIRTIS was one of the experiments on board the European mission Venus Express [10]. It consisted of two channels: VIRTIS-M and VIRTIS-H. For this study, we will analyze the complete VIRTIS dataset acquired between December 2006 and January 2010 [11,12]. References [1] Sanchez-Lavega, A. et al. (2017) Space Science Reviews, Volume 212, Issue 3-4, pp. 1541-1616. [2] Goncalves R. et al. Atmosphere, 12:2., 2021. doi: 10.3390/atmos12010002. [3] Hueso, R. et al. (2012) Icarus, Volume 217, Issue 2, p. 585-598. [4] Sornig, M. et al. (2013) Icarus 225, 828–839. [5] Rengel, M. et al. (2008) PSS, 56, 10, 1368-1384. [6] Piccialli, A. et al. A&A, 606, A53 (2017) DOI: 10.1051/0004-6361/201730923 [7] Newman, M. et al. (1984) J. Atmos. Sci., 41, 1901-1913. [8] Piccialli A. et al. (2008) JGR, 113,2, E00B11. [9] Piccialli A. et al. (2012) Icarus, 217, 669–681 [10] Drossart, P. et al. (2007) PSS, 55:1653–1672 [11] Grassi D. et al. (2008) JGR., 113, 2, E00B09. [12] Migliorini, A. et al. (2012) Icarus 217, 640–647. ​​​​​​​

 

Exoplanets with JWST/NIRSpec: Lessons learned from a year of operations
Tim Rawle (ESA), Stephan Birkmann, Catarina Alves de Oliveira

The Near-Infrared Spectrograph (NIRSpec) is one of four focal plane instruments onboard the James Webb Space Telescope (JWST), launched on 25 December 2021. After more than a year of stunningly successful operations, we present an overview of initial results from the NIRSpec Bright Object Times Series (BOTS) mode, primarily used for transit/eclipse observations of exoplanets. We will also highlight a few lessons learned from JWST operations, pertinent for future exoplanet missions such as ESA's Ariel. ​​​​​​​

 

The effect of metallicity on the CH4 and CO quenched abundance in H-dominated atmospheres
Vikas Soni (Physical Research Laboratory), Vikas Soni (First author), Kinsuk Acharyya (co-author)

Exoplanets show astonishing diversity in their parameter space, including atmospheric metallicity, which significantly affects the atmospheric composition. The effect of metallicity on the thermochemical equilibrium of exoplanet atmospheres has been studied widely. However, the effect on the disequilibrium abundance in the presence of transport (transport abundance) is largely unexplored and has only been studied for some targeted exoplanets. There are many available methods to find the transport abundance. Among these methods, the quenching approximation is the most straightforward way to constrain the transport abundance. In the quenching approximation, the quench level is defined at a pressure level where the chemical and mixing time scales become equal. Above the quench level, the transport abundance is given by the equilibrium abundance at the quench level (quenched abundance). We studied the effect of metallicity on the chemical and vertical mixing timescales for a large parameter space of pressure, temperature, and metallicity (0.1 mbar to 1 kbar, 500-2500 K, 0.1-1000 x solar metallicity). We compute the thermochemical equilibrium abundance for our parameter range and use it to mark the rate-limiting step (RLS) in a reduced chemical network. For this task, we built a network analysis tool to find the RLS and conversion scheme for a given set of molecules. By comparing the calculated mixing time scale and chemical time scale, we find all possible quench level data points in our parameter range and study the effect of metallicity on the location of the quench level. Our equilibrium results are in good agreement with the literature. The CO-CH4 and CO-CO2 equal-abundance curves move to low-temperature and high-temperature, respectively, with increasing metallicity. The abundance of CO and H2O increases linearly, whereas CO2 increases as the square of the metallicity. However, the CH4 abundance increases with metallicity only in the low-temperature and high-pressure regions, where it is a major source of C. The chemical time scale of CO is a weak function of metallicity; however, the chemical time scale of CH4 decreases linearly with increasing metallicity. By comparing the chemical time scale with the mixing time scale, we find that the quenched level of CO moves deep in the atmosphere with increasing metallicity and the CH4 quench level is a complex function of metallicity. For the benchmarking of quenched abundance, we compared the output of an in-house developed full transport chemical kinetics model with the output of the quenching approximation for two test exoplanets. The quenching approximation is accurate within an order of magnitude (which can be further improved by using the mixing length instead of the scale height). We also take three test exoplanets, HR 8799 b, HD 189733b, and Gj 436-b, and find that the quench level data points constrain exoplanets mixing strength and atmospheric metallicity for these exoplanets. Thus, the quench level data points and observed abundance of molecules can be a powerful tool to constrain atmospheric parameters. ​​​​​​​

 

Atmospheric turbulence and magnetic field amplification in hot Jupiters
Clàudia Soriano Guerrero (Institute of Space Sciences)

This project discusses the peculiar class of exoplanets called Hot Jupiters (HJs), which are gas giants orbiting very close to their host stars. These planets have inflated radii that cannot be accounted for standard cooling models for planetary evolution. Various possible mechanisms have been proposed, among which is Ohmic dissipation based on the dissipation of currents induced by the magnetic field stretching due to the flow motion. This project focuses on the effect of atmospheric turbulence on magnetic fields and Ohmic dissipation in the upper atmosphere of HJs. Box simulations representing tiny atmospheric columns are used to evaluate where electrical currents are induced by the shear layer and the turbulence and quantify them. We aim to extend previous studies to the ideal magnetohydrodynamic (MHD) regime applicable for high enough conductivities, for very Hot Jupiters. We evaluate the amplifications of the magnetic field and current profile at equilibrium, and study the effects of enforcing turbulent perturbations in addition to the zonal wind in the upper atmosphere. We include realistic profiles for the wind velocity, taking into account more recent results about zonal winds in global circulation models. In conclusion, the simulations performed in this study suggest that the strong electrical currents generated are enough to explain the inflated radii of very Hot Jupiters, if they penetrate inner layers of the planet. ​​​​​​​
 

Can wave-particle interaction be important for ion heating and escape at Venus?
Gabriella Stenberg Wieser (Swedish Institute of Space Physics, Kiruna, SWEDEN), Mats André, Hans Nilsson

Wave-particle interaction has been identified as a major ion energization process at Earth. A common type of ion heating is associated with low-frequency broadband electric wave fields. The spectral density of such broadband waves does not exhibit a peak at a certain frequency but the wave power available at the ion gyrofrequency may nevertheless efficiently energize the ions. At Earth this heating mechanism is definitely effective and important. Venus lacks an intrinsic magnetic field and the induced magnetosphere much smaller. The interaction with the solar wind is very different from the terrestrial case and the role of wave-particle interaction has not been much explored. We investigate if ion energization by electric wave power is important also at Venus and compare with the Earth case.

 

 

High-resolution transmission spectroscopic studies of hot and ultra-hot Jupiters
Monika Stangret (INAF - OAPd, Italy)

Hot and ultra-hot Jupiters, gas-giant planets with short orbital periods, and hot, extended atmospheres, are the most suitable objects in order to study the chemical composition of the atmospheres using emission and transmission spectroscopy. Their tidally-locked nature leads to big differences between night and day side temperatures, and in consequence differences the atmospheric chemical composition of both terminators. Thanks to a new generation of high-resolution ground-based spectrographs such us HARPS-N, HARPS, CARMENES, and ESPRESSO, we are able to perform those studies. In my poster, I want to present a complex analysis of the chemical composition of a set of hot and ultra-hot Jupiters using high-resolution spectroscopic observations. Using the cross-correlation method and transmission spectroscopy around single lines, we searched for a set of atoms and molecules in the atmosphere. Additionally, by analyzing the Rossiter-McLaughlin effect we measured the obliquity of those systems. Our work determines the temperature in which we differentiate between the hot and ultra-hot Jupiters, and show the importance of complex studies of those object using broad sets of chemical species model. ​​​​​​​

 

Martian Atmospheric Chemistry of HCl: Implications for the Lifetime of Atmospheric Methane
Benjamin Taysum (Deutsches Zentrum für Luft- und Raumfahrt, Institute of Planetary Research), Paul I. Palmer, Mikhail Luginin, Nikolay Ignatiev, Alexander Trokhimovskiy, Alexey Shakun, Alexey Grigoriev, Franck Montmessin, Oleg Korablev, Kevin Olsen

We develop a 1-D atmospheric photochemistry model for Mars to interpret hydrogen chloride (HCl) profile measurements collected by the ACS MIR spectrometer aboard the ExoMars Trace Gas Orbiter (TGO) in Mars Year (MY) 34. We include a gas-phase chlorine chemistry scheme and study 1) surface chemistry, 2) hydrolysis, 3) photolysis, and 4) hydration and photolysis of dust grains as possible sources of gas-phase chlorine chemistry. Heterogeneous uptake of chlorine species onto water ice and minerals in Martian dust are loss processes common to all mechanisms. We drive the 1-D model using TGO profile measurements of aerosols and water vapour. We find that mechanism four can reproduce observed HCl profile tendencies during MY34. It reproduces the HCl cut-off at high southern latitudes (< 60°) at ~35 km, and forms layers of HCl between 20-35 km at the tropics. Mechanisms one, two, and three result in significant model biases. % Seasonal variations of Martian HCl are reproduced by mechanism four, yielding low HCl abundances (< 1 ppb) prior to the dust season that rise to 2-6 ppb in southern latitudes during the dust season. We find that the additional Cl atoms released via mechanism four shortens the atmospheric lifetime of methane by a magnitude of 10^2. This suggests the production of Cl via the UV (or other electromagnetic radiation) induced breakdown of hydrated perchlorate in airborne Martian dust, consistent with observed profiles of HCl, helps reconcile observed variations of methane with photochemical models. ​​​​​​​

 

Venus atmospheric circulation from the cloud features tracking in the VMC/ Venus Express images
Dmitrij Titov (Leiden Observatory, Leiden University), D. Titov, I. Khatuntsev, M. Patsaeva, N. Ignatiev

Global circulation of the Venus atmosphere is still one of unsolved fundamental problems in the planetary physics. Venus Express collected the longest time series of the planet images in several wavelengths from UV to near-IR that allowed to track winds at different levels within the cloud (50-70 km). Up to a half a million wind vectors were derived from the cloud features tracking. This provided complete characterization of the atmospheric circulation and its variability including changes with altitude, latitude, local solar time as well as influence of the surface topography and long term trends. The talk will present these results, outline potential complementarities with other data sets, and give an outlook for future missions in the coming "Venus Decade".​​ ​​​​​

 

Evolution of Titan's Stratospheric HCN in High Spatial Resolution
Lucy Wright (University of Bristol), Nicholas A. Teanby, Patrick G. J. Irwin

Saturn's largest moon, Titan, is the only moon in our solar system with a substantial atmosphere. Like Earth, Titan's atmosphere comprises mostly Nitrogen but is also host to many hydrocarbon and nitrile species, produced by photochemistry in the upper atmosphere. These species are good tracers of atmospheric dynamics. From 2004 to 2017, NASA/ESA's Cassini-Huygens spacecraft explored the Saturn system, performing 127 flybys of Titan. On its third flyby, Cassini released the ESA-operated Huygens atmospheric entry probe, which performed measurements on its descent to Titan's surface. Cassini's Composite Infrared Spectrometer (CIRS) observed Titan in the infrared for 13 years, almost half a Titan year. We use nadir observations acquired by the CIRS instrument at low spectral resolution to map trace species in Titan's stratosphere at high spatial resolution. In-situ measurements acquired by the Huygens probe constrain our atmospheric retrievals. We use trace gas distributions to investigate seasonal changes in dynamics near Titan's stratospheric equator. ​​​​​​​

 

Surface geological & geophysical processes

 

​​​​​​​A Comparison of Syndynic Bands in Long Period Comets
Qasim Afghan (UCL), Geraint H. Jones, Andrew Coates, Oliver Price

We have been analysing the dust tails of highly active comets using Finson-Probstein analysis e.g. Afghan et al. (2023). Observations of Comet NEOWISE (C/2020 F3) during its perihelion in July 2020 showed the presence of syndynic bands in the dust tail: bright bands that are accurately bounded by syndynes (lines of constant dust β). NEOWISE's dust tail was segmented into two bright bands, with a darker band in between them. Analysis using a Finson-Probstein model showed a bimodal distribution of dust grain β, where a large proportion of dust grains with β values of around β =1.63±0.02 and β =0.57±0.16 were ejected from the nucleus. The darker band would thus be a comparatively dust sparse region, corresponding to a lack of dust grains with 0.82< β <1.2. Similar syndynic band structures have been observed in other long period comets (LPCs), and the reason for this bimodal distribution is still unknown. This work analyses the syndynic band structures of several LPCs, including C/2020 F3 (NEOWISE), C/2006 P1 (McNaught), C/2011 L4 (PanSTARRS), and C/1995 O1 (Hale-Bopp). Comparisons of dust grain β distributions between the comets show strong agreement: the dust dense and dust sparse regions for these comets all have very similar dust β ranges. Furthermore, this comparison revealed a trimodal β distribution in the dust tails: upon further examination of Comet NEOWISE's dust tail, this third band is faintly visible and thus this comparison has improved on our previous C/2020 F3 study. This commonality between the syndynic bands in these comets suggest that there is some inherent common attribute of these comets that cause this structure. A possible mechanism for this structure, relating to the composition of these comets, is discussed. Afghan, Qasim, Geraint H. Jones, Oliver Price, Andrew Coates. 2023. 'Observations of a dust tail gap in comet C/2014 Q1 (PanSTARRS)'. Icarus 390. doi:10.1016/j.icarus.2022.115286 ​​​​​​​

 

Using photometry to better understand icy surfaces of our solar system
Ines Belgacem (ESA/ESAC), Thomas Cornet, Frédéric Schmidt, Jessica Hogan, François Andrieu, Guillaume Cruz Mermy

The icy moon of our solar system are promising candidates in the search for habitability. Using photometry, we want to better understand the history of these fascinating bodies and help identify potential areas of interest for future missions. The study of photometry - reflectance variation with respect to the geometry of observation - can help us better understand the processes at play at the surface. The photometry of a surface is intimately linked to its microtexture (roughness, shape of particles, porosity, ....), and can strongly affect all remote sensing observations if performed in varied geometric conditions. As a result, having a clear understanding of a surface photometry is the first step for any remote sensing applications such as surface mapping or spectroscopy. We have carried out regional studies of Jupiter's icy moons Europa and Ganymede as well as Saturn's moon Enceladus and compared the photometric parameters we obtained with known geological context. With this, we aim to better understand the link between photometry and physical properties of planetary surfaces and identify potential areas of interest for future missions. ​​​​​​​
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Diresct deposition of a water ice dependent mantle enabled by improved modelling of the recent Martian climate
Joesph Naar (Laboratoire de Météorologie Dynamique, UMR CNRS 8539, Institut Pierre-Simon Laplace, Sorbonne Universités, UPMC Univ Paris 06, 4 place Jussieu, 75005, Paris, France. ), F. Forget, E. Millour, A. Bierjon

Geologically recent glacial and periglacial landforms (<100 Myrs) are found on Mars at all latitudes. They are thought to have formed under different climate regimes than the present-day cold and arid Mars. Among these landforms, the water-ice “latitude-dependent mantle” is thought to be only a few hundred thousand years old, therefore as a result of the latest high obliquity excursion up to 35°(in comparison with today’s 25°). With this orbital forcing, the increased insolation on top of the northern polar cap strongly enhances the amount of water in the martian atmosphere. However previous studies aiming at modeling the martian atmosphere at an obliquity of 35° and assuming a permanent reservoir at the north pole like today could not explain how ice could have accumulated outside the polar regions. In these previous studies, the radiative effect of water-ice clouds was not accounted for, which was acceptable in the current martian climate. But previous work using the Mars Planeraty Climate Model (PCM, previously Mars LMD-GCM) demonstrated that their effect becomes preponderant at high obliquity, when the atmospheric humidity is greatly increased. Radiatively active clouds warm the atmosphere and enhance the meridional circulation and transport of water. Following this work, we have improved our representation of water-ice cloud using a temperature-dependent nucleation scheme. In addition, we now take into account the latent heat of sublimation of ground water ice, which is negligible in present-day martian climate. The associated cooling limits summertime sublimation of the northern polar cap but also of the mid-latitude ice deposits. Mid-latitude ice deposits forms in winter at high obliquity through snow precipitation. We study the influence of an increased ice albedo (up to 0.7) accounting for ice freshness on the summer sublimation. Our simulations are performed simply by shifting the obliquity of Mars to 35°, with the northern polar cap as the main atmospheric water reservoir and considering clear sky dust conditions all year long. We find that under the exotic climate at 35° obliquity driven by the radiatively active water-ice clouds, the combination of latent heat of surface water ice and increased albedo allows for a perennial deposition of ice in the mid-latitudes, with yearly accumulation rates consistent with the formation of the latitude dependent mantle.

 

Interior structure & processes

 

Terrestrial Exoplanet Internal Structure Constraints Are Not Limited by Host Star Spectroscopic Analyses
Alejandro Ross (Johns Hopkins University), Henrique Reggiani, Kevin C. Schlaufman, Mykhaylo Plotnykov, Diana Valencia

Exoplanet mass and radius inferences, and therefore internal structure constraints, are based on host star mass and radius inferences. Accurate, precise, homogeneous, and self-consistent exoplanet internal structure constraints therefore demand accurate, precise, homogeneous, and self-consistent host star mass, radius, and elemental abundance inferences. Published terrestrial exoplanet internal structure constraints have often been based on host star mass, radius, and elemental abundance inferences that are not self-consistent. For 20 solar-type stars known to host terrestrial exoplanets, we use all available astrometric and photometric data plus high-resolution optical spectroscopy to infer accurate, precise, homogeneous, and self-consistent photospheric and fundamental stellar parameters as well as elemental abundances. We infer updated planetary masses and radii using these data plus Doppler and transit observables and then use our complete data set to derive the strongest possible constraints on the internal structures of these terrestrial planets. We repeat these same analyses using the high-quality catalogs of photospheric stellar parameters and elemental abundances from SDSS DR17 APOGEE and Brewer et al. (2016, 2018) to assess the impact of differing photospheric stellar parameters and elemental abundance inference approaches on terrestrial exoplanet internal structure modeling. ​​​​​​​

 

Tidal heating in Io drives non-symmetric volcanic pattern
Wouter van der Wal (Delft University of Technology), Teresa Steinke, Marc Rovira-Navarro

Jupiter's moon Io is home to widespread volcanism that has been observed by satellite missions and earth-bound telescopes. A compilation of such data shows an offset in volcanic activity of about 30 degrees with respect to the meridian crossing the sub-Jovian point (prime meridian). Although tidal dissipation is the main heat source for Io, tidal dissipation based on symmetric models of Io can not explain the observed offset. However, tidal heating may lead to spatially varying viscosity in Io's sub-surface which feeds back on the tidal dissipation. Here, we investigate whether this feedback can cause the observed offset in volcanic activity. We model tidal dissipation in Io using a finite element model. Temperature, melt fraction and viscosity are calculated assuming that most heating takes place in the asthenosphere and that viscosity is controlled by the melt fraction. The simulation results in a spatial variation in viscosity and hence response time. We calculate a new tidal heating pattern for the viscosity field and iterate until an equilibrium is reached. The final heating pattern has an offset of 15 degrees, which is less than but a significant part of the observed offset. Since our assumptions can be valid for the general case of a rocky moon orbiting close to its central body, our results suggest that exomoons which experience strong tidal dissipation will always exhibit an asymmetric heating pattern. This could lead to strong hotspots and plumes, which improve the chance of the exomoons' detection. ​​​​​​​

 

Exploring Jupiter's structure using a combination of interior and wind models
Maayan Ziv (Department of Earth and Planetary Sciences, Weizmann Institute of Science, Israel), Eli Galanti, Saburo Howard, Tristan Guillot, Yohai Kaspi

The interior structure of Jupiter holds information on its formation and evolution processes, with the two research fields highly related to one another. The range of plausible interior structures is constrained by the gravity field measured by the Juno mission to an exquisite precision, the Galileo probe that measured atmospheric abundances and the 1 bar temperature, and the surface winds and their decay profile which have a significant contribution to the gravity field. Most interiors models consistent with Juno's measured gravity moments are agreeing on the presence of a dilute core in Jupiter, but with the cost of discrepancies with Galileo atmospheric observations. Examining the relations between different model parameters is key for finding effective parameters and objectively revealing the parameter combination reproducing the measurements. Here, we use the concentric MacLaurin spheroid method to generate interior models, coupled to an atmospheric model matching the measured abundances and temperatures. Starting from a basic interior solution reproducing Juno's measurements, with a realistic cloud-level wind profile, we explore the relations between different model parameters, identifying solutions search paths, and showing limitations in obtaining solutions fitting to both Juno's and Galileo's observations. ​​​​​​​

 

CuRrent and Future missions

 

The Ariel Science Operations Centre
Catarina Alves de Oliveira (ESA)

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was selected as the fourth medium-class mission in ESA's Cosmic Vision programme. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. A Science Operations Centre (SOC) located at the European Space Astronomy Centre (ESAC), in Madrid, Spain will be provided by ESA. This contribution summarizes its main responsibilities, including the distribution of data products to the scientific community. ​​​​​​​

 

The PLATO Mission
Heike Rauer (Institute of Planetary Research, DLR and FU Berlin), C. Aerts, KU Leuven, M. Deleuil, LAM, L. Gizon, MPI for Solar System Research, M. Goupil, LESIA/Observatoire de Paris, A. Heras, ESA, M. Mas-Hesse, CSIC/INTA, I. Pagano, INAF, G.P. Piotto, Univ. Padova, D. Pollacco, Univ. Warwick, R. Ragazzoni, INAF, G. Ramsay, Armagh Obs., S. Udry, Univ. Geneva

PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission and designed to detect and characterize extrasolar planets by high-precision, long-term photometric and asteroseismic monitoring of a large number of stars. PLATO will detect small planets around bright stars, including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observation from ground, planets will be characterized for their radius, mass, and age with high accuracy. PLATO will provide us the first large-scale catalogue of well-characterized small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our solar system planets in a broader context. PLATO will study host stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. PLATO is scheduled for a launch date end 2026. Following the successful Critical Milestone Review, ESA has given green light for the implementation of the spacecraft and the payload, which includes the serial production of its 26 cameras. This presentation will give an overview of the PLATO science goals, of its instrument and mission profile status. ​​​​​​​

 

The M-MATISSE mission: Mars Magnetosphere ATmosphere Ionosphere and Space weather SciencE. An ESA Medium class (M7) candidate.
Beatriz Sánchez-Cano (School of Physics and Astronomy, University of Leicester, United Kingdom), François Leblanc, David Andrews, Nicolas Andre, Andrew Coates, Raffaella D'Amicis, Johan De Keyser, Yoshifumi Futaana, Lina Hadid, Pierre Henri, Gunter Laky, Hiromu Nakagawa, Martin Pätzold, David Pisa, Ferdinand Plaschke, Jim Raines, Hanna Rothkaehl, Štěpán Štverák, Ed Thieman, Daniel Verscharen, Tom Woods, Shoichiro Yokota

The "Mars Magnetosphere ATmosphere Ionosphere and Space-weather SciencE (M-MATISSE)" mission is an ESA Medium class (M7) candidate currently in Phase 0 study by ESA. M-MATISSE's main scientific goal is to unravel the complex and dynamic couplings of the Martian magnetosphere, ionosphere and thermosphere (MIT coupling) with relation to the Solar Wind (i.e. space weather) and the lower atmosphere. It will provide the first global characterisation of the dynamics of the Martian system at all altitudes, to understand how the atmosphere dissipates the incoming energy from the solar wind, including radiation, as well as how different surface processes are affected by Space Weather activity. M-MATISSE consists of two orbiters with focused, tailored, high-heritage payloads to observe the plasma environment from the surface to space through coordinated simultaneous observations. It will utilize a unique 3-vantage point observational perspective, with the combination of in-situ measurements by both orbiters and remote observations of the lower atmosphere and ionosphere by radio crosstalk between them. M-MATISSE is the product of a large organized and experienced international consortium. It has the unique capability to track solar perturbations from the Solar Wind down to the surface, being the first mission fully dedicated to understand planetary space weather at Mars. It will revolutionize our understanding and ability to forecast potential global hazard situations at Mars, an essential precursor to any future robotic & human exploration. ​​​​​​​

 

Mars' ionosphere: The bond between the lower atmosphere and space
Beatriz Sanchez-Cano (School of Physics and Astronomy, University of Leicester, United Kingdom), Mark Lester, Olivier Witasse, Herman Opgenoorth, David Andrews, Rob Lillis, Pierre-Louis Blelly, Marco Cartacci, Roberto Orosei, Dikshita Meggi, Katerina Stergiopoulou, Simon Joyce

For planets without a global intrinsic magnetic field, the ionosphere is the conducting layer of the atmosphere that is mostly the result of solar EUV photoionization. It is also the layer that connects the neutral atmosphere with space and acts as the main obstacle to the solar wind. The ionosphere's interaction with the solar wind is, therefore, a critical factor for understanding atmospheric evolution of unmagnetised or nearly unmagnetised planets, but also for planetary exploration as it has an impact on current technology deployed on each planet. In this talk, I will present our current knowledge on Mars ionosphere and how it behaves with respect to energy inputs from the solar wind (Space Weather) as well as from the lower atmosphere and how the entire system behaves. In particular, I will focus on recent advances in the understanding of the ionospheric reaction to different Space Weather events during the solar cycle, both from the data analysis and ionospheric modelling perspectives. Some important aspects to consider are the plasma boundaries of the system, the thermosphere-ionosphere coupling, as well as the effect of electron precipitation from large Space Weather events in the lower Martian ionosphere. Finally, I will give my perspective on some of the key outstanding questions that still remain unknown but are part of the next generation of Mars' ionospheric science and exploration, which explains the actual need for multi-spacecraft missions at Mars such as the ESA under evaluation M-MATISSE mission. ​​​​​​​

 

Ice Giant Missions as Gravitational Wave Detectors
Deniz Soyuer (University of Zurich), Lorenz Zwick, Daniel D'Orazio, Prasenjit Saha

The past year has seen many papers underlining the significance of a space mission to Uranus and Neptune. Proposed mission plans usually involve a ~10 year cruise time to the ice giants. This cruise time can be utilized to search for low-frequency gravitational waves (GWs) by observing the Doppler shift caused by them in the Earth-spacecraft radio link. We calculate the sensitivity of prospective ice giant missions to GWs in comparison to former planetary missions which searched for GWs. Then, adopting a steady-state black hole binary population, we derive a conservative estimate for the detection rate of extreme mass ratio inspirals (EMRIs), supermassive- (SMBH) and stellar mass binary black hole (sBBH) mergers. For a total of ten 40-day observations during the cruise of a single spacecraft, approximately 0.5 detections of SMBH mergers are likely, if Allan deviation of Cassini-era noise is improved by ~10^2 in the 10^-5 - 10^-3 Hz range. For EMRIs the number of detections lies between O(0.1)-O(100). Furthermore, ice giant missions combined with the Laser Interferometer Space Antenna (LISA) would improve the GW source localisation by an order of magnitude compared to LISA by itself. With a significant improvement in the total Allan deviation, a Doppler tracking experiment might become as capable as LISA at such low frequencies, and help bridge the gap between mHz detectors and Pulsar Timing Arrays. Thus, ice giant missions could play a critical role in expanding the horizon of gravitational wave searches and maybe even be the first to detect the first SMBH merger.

 

Solar energetic particle events detected with housekeeping sensors by Mars Express, Trace Gas Orbiter, Gaia, Rosetta, BepiColombo and Solar Orbiter
Olivier Witasse (European Space Agency), Beatriz Sanchez-Cano, Elise W. Knutsen, Dikshita Meggi, Mark Lester, Robert F. Wimmer-Schweingruber, Marco Pinto and the ESA mission teams.

While space weather has been a growing field of research and applications over the last 15-20 years, "planetary space weather" is an emerging discipline. In fact, as long as we expand our robotic exploration within the Solar System, monitoring planetary space weather is becoming more necessary than ever, especially to understand the input of energy into a planetary system. Despite this, not every spacecraft is designed for Space Weather science and only a few of them have the necessary particle instrumentation for Space Weather purposes. However, all of them have thousands of housekeeping detectors distributed along the spacecraft. In particular, energetic particles impact detectors and subsystems on a spacecraft and their effects can be identified in selected housekeeping data sets, such as the Error Detection And Correction (EDAC) counters. In this study, we investigate the use of these engineering datasets for scientific purposes by performing the first feasibility study of solar energetic particle detection using EDAC counters from several available ESA Solar System missions, i.e. Mars Express, Trace Gas Orbiter, Gaia, Rosetta, BepiColombo and Solar Orbiter. In order to validate the results, these detections are compared to other observations from scientific instruments on board these missions. Moreover, the potential implications of Space Weather detections based on EDAC sensors at Mars and Comet 67P/Churyumov-Gerasimenko is analyzed. This study has the potential to provide a good observation network for large solar particle event at locations where no dedicated scientific instruments are available. ​​​​​​​