From Alluvial Fans to Deltas: the Sedimentary history of Mars as Seen from the HRSC (Mars Express)

Ori, Gian Gabriele¹, Gerahrd Neukum², Monica Pondrelli³, Ernst Hauber⁴ (1) IRSPS, Pescara, Italy (2) Freie Universitet, Berlin, Germany (3) IRSPS, Pescara, Ivory Coast (4) DLR, Berlin, Germany

A large number of sedimentary processes have shaped the surface of Mars. A large portion of these processes is related with the flowing of water and the accumulation of sediment into basins (dry or standing bodies of water). Alluvial fan and fan deltas have been recognised in the decade including Gilbert-type deltas. These systems debouch in complex basins. Large deltas with well-defined delta plains consisting of distributary channels are present in several locations. The camera (HRSC) on board of Mars Express bears remarkable stereo capabilities and allows the analysis of stratification patterns and 3D analysis. Therefore, besides the simple morphological analysis, it is possible to understand the stratigraphic evolution of facies and environments. Several deltas present well-defined delta fronts with the development of clinoforms. Stratigraphic patterns show the evolution of the water bodies with, often, lowering of the water bodies. Alluvial fans are linked to dry conditions and sometime they are interbedded in the distal part with sebkha-like deposits. This view of Mars shows a complex plant where a host of sedimentary processes developed and shaped the surface. This complexity implies that the geological history of the planet is not at all understood. It would be advisable produce geological analysis based on data sets rather than schemes and models of the evolution of the entire body based on scanty data sets.