ENDMEMBER IDENTIFICATION AND CHARACTERIZATION OF MARTIAN METEORITES WITH MICROIMAGING INFRARED SPECTROSCOPY

Martian meteorites represent a significant source of spectral information that is largely unexplored. These samples provide the opportunity to conduct laboratory analyses that link grain-scale petrologic observations to remotely sensed and in-situ observations on Mars. Understanding the spectral diversity of the mafic mineralogy present in the Martian meteorites will help with the interpretation of similar spectra from Martian igneous terrains, especially younger Amazonian volcanic provinces including Tharsis and Elysium. Using the Ehlmann Lab Imaging Spectrometer (ELIS) at Caltech and the Ultra-Compact Imaging Spectrometer (UCIS) at JPL, we have collected 171 shortwave infrared hyperspectral images of 57 different Martian meteorites. Petrologic classes of meteorites represented in the dataset include 2 chassignites, 6 nakhlites, 47 shergottites, 1 polymict breccia, and 1 orthopyroxenite. Each image cube has a spectral range of 1-2.5 μm, spectral resolution of 6 nm, and spatial resolution of 212 μm/pixel (ELIS) or 80 μm/pixel (UCIS). In total, 1,346,818 unique spectra were collected for the suite of Martian meteorites, representing a comprehensive dataset of spectral diversity for the Martian meteorites. With this robust dataset of meteorite spectra, endmember spectra representing the major minerals present in the Martian meteorites (primarily olivine and pyroxenes) were identified and characterized. Here, we will present our processing pipeline for identifying endmember spectra within and between Martian meteorite classes and for defining spectral classes, which differ from and expand upon traditional petrologic classes. In addition, we document the Fe/Mg/Ca compositional variability within olivine and pyroxenes, tracking solid solution chemistry using characterization of spectra features that include the olivine 1-μm feature and pyroxene 1-μm and 2-μm features. These endmembers represent the spectral diversity of Martian mafic and ultramafic meteorites, which constrain remotely identified spectra from Mars beyond basic mineralogy, including identification of lithologies with characteristic assemblages and minor mineral phases that may not be uniquely identifiable in orbital spectra.