THE SUBSURFACE GEOLOGY OF MARS VIA REMOTE SENSING OF IMPACT CRATERS

Impact craters provide natural exposures of subsurface composition, stratigraphy and, in some cases, geologic features that are not otherwise exposed at the surface (e.g., uplift, rifting, tectonics, etc.). Remote sensing of craters on the Moon, Earth and Mars have been used to effectively capture a natural glimpse of the subsurface geology and provide some additional insight into the differentiation and petrogenetic history of these terrestrial bodies. These studies indicate that stratigraphic relationships and compositional changes with depth, as exposed in crater morphologic features (i.e., central uplifts, crater walls/terraces, and ejecta), may be ascertained from remote sensing data with at least moderate (~100-m/pixel) spatial resolutions.

The purpose of this Mars-based study is two-fold: 1) to use infrared data from the Thermal Emission Imaging System (THEMIS) and the Thermal Emission System (TES) to map and spectrally identify mineral or lithologic units on Mars that are exposed by craters, and 2) use all available visible-wavelength imagery (e.g., THEMIS visible, Mars Orbiter Camera [MOC], etc.), TES-albedo, thermal inertia data, topographic data (i.e., Mars Orbiter Laser Altimeter [MOLA]) and crater-scaling observations to make geologic interpretations of geologic structures that are exposed in crater morphologic features.

One or as many as six craters within Isidis Planitia, Meridiani Planum, Acidalia Planitia and Thaumasia Planum, have been mapped bearing spectrally distinct crater-units. These units were mapped using 8-thermal infrared bands from THEMIS and have 1:1 correlations with crater morphologic features as observed in visible-imagery. Layered-bedrock can often be observed in high-resolution MOC images of these craters, which in some cases were subjected to rotation, folding and faulting. In one case, layers from as deep as ~5 km beneath the surface can be observed in unnamed crater in Thaumasia Planum. Crater observations such as these will hopefully give us insight into the geologic origin of these regions and may potentially have global implications for the petrogenesis of the Martian crust.