No abstract

Silica has the highest demonstrated potential of any phase to preserve microfossils on Earth and therefore may host potential biosignatures on Mars. We detected hydrated silica in Jezero crater, the landing site of the National Aeronautics and Space Administration's Mars 2020 rover mission, by applying Dynamic Aperture Factor Analysis/Target Transformation to images from the Compact Reconnaissance Imaging Spectrometer for Mars. Hydrated silica detections with Dynamic Aperture Factor Analysis/Target Transformation were verified using commonly accepted Compact Reconnaissance Imaging Spectrometer for Mars analysis methods. The morphology of geologic units associated with silica was characterized with high‐resolution imaging. Several hypotheses are presented for the formation environment of hydrated silica. All are testable via in situ investigation. We assess the likelihood of silica to preserve biosignatures in these different scenarios based on habitability considerations and biosignature preservation in Earth analog environments and materials. Also reported are possible detections of hydrated silica in the Nili Fossae basement and olivine‐rich units, as well as Al‐phyllosilicate within Jezero crater.

Olivine ([Mg,Fe] 2 SiO 4) has been remotely detected on numerous solar system bodies, but its composition has been only partially constrained using visible-near infrared (VNIR, 0.5-3 μm) and midinfrared (MIR, 8-15 μm) spectra. Meanwhile, the spectral character of olivine in the "cross-over" region of the infrared (4-8 μm) remains generally unexplored. We examine the relationship between olivine Mg# (molar Mg/[Mg + Fe] × 100) and the wavelength positions of two strong, discrete overtonecombination bands at~5.6 and~6.0 μm. In reflectance and thermal emission spectra measured for 47 synthetic and natural olivine samples that span the Mg-Fe solid solution, we find that the 5.6 and 6.0 μm bands shift systematically to longer wavelengths by 0.11 and 0.10 μm, respectively, with increasing Fe content. Our results indicate that olivine Mg# may be determined within ±10 mol% forsterite using the positions of these two bands, making "cross-over" region spectroscopy a potentially powerful remote sensing tool.