GRAVITY-DRIVEN DIFFERENCES IN FLUVIAL SEDIMENT TRANSPORT ON MARS AND EARTH - LISSANE BRAAT

There is abundant evidence from fluvial landforms and deposits that early Mars had rivers that actively transported sediment and shaped its surface. Preserved ancient landscapes altered by water provide valuable insights into past processes on the planet’s surface and the presence of water. To better understand these landforms, we rely on knowledge gained from systems on Earth. However, is it fair to do so when the gravity on Mars is much lower? How does gravity affect sediment transport and the landforms created by water? In this study, we isolate the effect of gravity on sediment transport by water with an analytical river model. We used 32 sediment transport formulas to compare sediment transport rates on Earth and Mars for the same conditions except gravity. The results show that larger grains are picked up by the flow on Mars and the transport rate of sediment travelling in suspension is higher, and therefore total transport as well. Because grains transported near and on the bed are less affected than the grains in suspension, the effect of gravity varies with the way of transport and hence grain size. Therefore, gravity-driven differences in sediment transport by water should produce differences in sediment sorting, morphology and stratigraphy between Earth and Mars.