ACCOUNTING FOR SPECTRAL MASKING IN IMAGING SPECTROSCOPY OF MARTIAN OUTCROPS CONTAINING FERRIHYDRITE

Spectral masking poses major complications to visible- to near-infrared imaging spectroscopy of the Martian surface. The presence of “masking minerals” even in small abundances can prevent visible- to near-infrared (VNIR) spectrometers such as the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) from accurately determining mineralogical compositions of the outcrops it maps. For example, ferrihydrite [‎(Fe3+)2O3•0.5H2O] is known to mask goethite [α-FeO(‎OH‎)] in the VNIR; however, the relative abundances of the minerals needed to achieve masking are unknown. Here, we address this problem by synthesizing pure endmembers of ferrihydrite and goethite then mixing them in varying ratios to determine the masking relationships between the two minerals. This work is intended to facilitate more accurate predictions of the relative amounts of minerals in Martian deposits and subsequently, mineralogists will be able to further constrain inferences of past Martian environments.