Multi-spacecraft synergy with MEX HRSC and MRO SHARAD: Light-Toned Deposits in crater bulges

Abstract

Light-toned deposits (LTDs) occur extensively on Mars. Several of them have been imaged by the Mars Express (MEX) High Resolution Stereo Camera (HRSC), adding 3-D information to the available large extent of datasets from several missions. (e.g. MGS, Odyssey, MRO). Although LTDs are often located in steep and rough areas (e.g. Valles Marineris, chaotic terrains), the use of HRSC high-resolution Digital Elevation Models (DEMs) greatly helps the analysis of ground penetrating radars such as Mars Reconnaissance Orbiter (MRO) Shallow Radar (SHARAD). We are concentrating on various craters with bulges in Arabia Terra (e.g. Crommelin) We built a Digital Elevation Model (175 m/pixel) covering the entire area or Crommelin crater and its neighbor in order to better simulate the surface clutter. LTDs in Crommelin crater have a thickness ranging from 1.5 to 2 km, and the crater just south of Crommelin shows comparable thickness. The deposits are finely stratified and they are affected by a variable amount of erosion. The morphology and structure of the deposits cropping out within the craters show a complex interplay between primary deposition, possible deformation and erosion, increasing the spatial variability of LTDs surface expression. Therefore the surface geology of Crommelin is rather complex, which suggests that its subsurface could be comparably complex. The relatively close distance between these LTDs and Meridiani Planum, which is characterized by the presence of LTDs that share several features with those in Crommelin offers the possibility of a comparison, not only on the surface geology and geomorphology of the two areas, but also on their subsurface radar expression, possibly useful to draw comparisons and distinctions between them. We plan to extend the synergic observation campaign to further areas where extensive (and relatively rough/steep) LTDs are present: this include other crater bulges, such as Gale, close to the dichotomy boundary, and few case studies of LTDs in the Valles Marineris canyon system. Although the choice of targets is challenging, the use of high resolution DEMs will hopefully provide better chances to detect subsurface echoes.