Analysis of Martian Parental Melts and Thermal Infrared Studies of Putative Paleolake Basins on Mars

Both martian meteorites and remote sensing data allow us to study the geologic history of Mars. Martian meteorites can reveal information regarding partial melting of the Mars mantle and the surface processes that affected the meteorite following eruption (weathering, impact ejection, etc.). Remote sensing data can be used to investigate the local-, regional- or global-scale surface of Mars in terms of composition and geomorphology. A well-rounded approach is necessary to address fundamental questions regarding the geologic history of Mars.

We studied melt inclusions in augite of the martian meteorite Nakhla to better understand the magma that produced this rock. This study used laboratory methods developed at the Virginia Tech Fluids Research Lab, electron microprobe analyses, and MELTS crystallization modeling. The result of this study was a new estimate of the Nakhla parent magma composition, which is basaltic in composition. Crystallization modeling of this composition provided the closest match to mineral abundances and composition observed within the nakhlites, suggesting an improved estimate.

In addition, we studied thermal infrared data of martian craters that some workers suggest display geomorphic evidence that they once contained lakes. If in fact these craters did hold water, they may still contain evaporite minerals deposited in this environment and detectable within the thermal infrared. We used data acquired by TES (Thermal Emission Spectrometer aboard the Mars Global Surveyor) and THEMIS (Thermal Emission Imaging System aboard Mars Odyssey). Because of its higher spatial resolution, THEMIS is best viewed as a spectral unit mapper, whereas TES is better at mineral identification because of its higher spectral resolution. Both studies employed a linear deconvolution routine developed at Arizona State University, spectral ratios and newly-developed carbonate indices to search for local-scale deposits of evaporites within craters. In these studies, we did not find mineralogic evidence supporting a paleolake origin for the surficial deposits within any crater.