Characterization of the Weathering Products of Antarctic Martian Meteorite Analog Materials and Implications for the Formation of Martian Surface Fines

Layered and massive outcrops on Mars, some as thick as 4 km, display the geomorphic attributes and stratigraphic relations of sedimentary rock. Sequences in some locations imply a dynamic depositional environment during early martian history. Subaerial (such as aeolian, impact, and volcani-clastic) and subaqueous processes may have contributed to the formation of the layers. Affinity for impact craters suggests cominance of lacus-trine deposition, alternatively, the materials were deposited in a dry, subaerial setting in which atmospheric variations mimicked a subaqueous depositional environment. The source regions and transport paths for the materials are not preserved. Introduction: Periodic concentric features named " honeycomb terrains " are observed in the NorthWestern part of Hellas (Fig. 1). These terrains cover the lowest part of the Hellas basin at elevations of –7 to –5 km, thus also the lowest points on Mars. Each " honeycomb cell " is about 5 to 10 km large. At MOC scale these features shows lot of deformed materials. Some authors speculate about possible ice blocks and soft muddy deformation to explain the formation of these concentric features [1]. In this study we show that the structural analysis of MOC images favors a ductile formation by doming inside a soft medium. Structural patterns typical of ductile shear zones are also observed. We discuss if this doming better correspond to salt diapirs or lower crustal tectonism. We propose that these features could correspond to ductile deformations similar to those observed on outcrops of the lower crust of the Archean period on Earth. Observations of structural domes: Figure 2 is located in the middle of the honeycomb terrains. The two concentric patterns correspond to two of the circular cells observed at larger scale. Their geometry can not be explained by the erosion of horizontal layers. Deformation in the zone T is on a flat surface. Patterns must be explained by structural deformation. The concentric feature in the lower part of the image shows foliation typical of flattening in the central part. This especially visible on E that may result from a sub-horizontal cross-section through the vertical axis of a dome. These concentric patterns correspond to a round shaped deformation of layers like those due to the intrusion of plutonic domes on Earth cut by erosion. So, in the following, by referring to " dome " we consider the structural pattern and not the topographic feature. Triangle zones are specific areas at the …