Reduced gravity effects on Martian deltaic sediment textures 

Sediment settling in water is driven by gravity and resisted by the drag of the liquid the particle has to pass through. In a given liquid, this drag is a function of settling velocity and subject to a complex relationship between particle movement and assocuated hydraulics of the liquid surrounding the particle. On Earth, settling experimets have been used to establish empirical relationships between settling velocity and properties such as particle size, shape and density. These relationships do not apply to conditions where settling velocity is reduced, e.g. because of lower gravity, such as Mars. In this study, the results of settling velocity measurements obtained during experiments on reduced gravity flights are used to assess the impact of reduced gravity on the sorting of sediment in a deltaic environment. The results show that sorting of the fine sand fraction is less pronounced than on Earth. This raises the question inasmuch terrestrial rocks with similar textures than those observed on Mars can be considered as an analogue for Martian sedimentary environments. The potential limitations of such analogues also affect the assessment of Martian sedimentary environments as either past habitats or archive for traces of past life on Mars.