Shortwave Infrared Microimaging Spectroscopy of the Martian Meteorites

Abstract Until samples from the Martian surface are successfully brought to Earth, meteorites represent the only opportunity to perform laboratory analyses on Martian material. Microimaging spectroscopy of the Martian meteorite suite provides a valuable means to better understand infrared data collected remotely from the Martian surface. This rapid and non‐destructive method surveys compositional and textural relationships within and between meteorite samples. We expand upon existing documentation of the spectral variability of the Martian meteorites by presenting a publicly accessible data set of over 1.2 million 1.0–2.5 μm spectra at 250 μm/pixel scale, from 144 imaged faces of 78 pieces of 54 distinctly named Martian meteorites. These meteorites include 2 chassignites, 6 nakhlites, 43 shergottites, 2 polymict breccias and 1 orthopyroxenite. Analysis of the spectral diversity results in the definition of 17 spectral classes on the basis of (a) color properties of the samples in false color with channels identified at spectrally significant wavelengths for mafic mineralogy, (b) a 3‐step classification process comprised of a two‐step unconstrained (orthogonal) Sequential Maximum Angle Convex Cone endmember extraction, Spectral Angle Mapping, and consolidation of the endmembers and their classified spectra into mineralogically significant groups, (c) band center position of the pyroxene 2 μm absorption, and (d) distribution and abundance of hydration/hydroxylation absorptions at 1.4 and 1.9 μm. Careful inspection of the spectra and processed data reveals compositional textures that are invisible to the naked eye, rare spectral phases, two distinct populations of high‐calcium pyroxenes, and evidence of secondary aqueous alteration.