The Mineralogical Diversity of Jezero’s Western Fan Revealed by SuperCam/IRS, Perseverance Rover, and Spectral Modeling
Résumé
The Perseverance rover is currently exploring the top of the western sedimentary delta/fan of Jezero Crater. The aim is to characterize the stratigraphy and mineral composition of this formation to provide geologic context and collect a representative set of core samples to be returned to Earth. Among the instruments aboard the rover, SuperCam plays a key role in this study thanks to its remote measurement capabilities, including the near-infrared reflectance spectroscopy performed by the infrared spectrometer (IRS). This instrument analyzes light reflected from rocks and soils in the 1.3 – 2.6 μm spectral range, with a 1.15 mrad field of view. The IRS is sensitive to the spectral signatures of primary and alteration minerals, enabling the analysis of the compositional diversity of rocks and thus to the study of their formation conditions. We present here the results of this instrument, including minerals identified through linear spectral modeling and their relationship with stratigraphy.
Linear spectral modeling fits a linear combination of library spectra on the IR spectra and allows estimates of the most likely mineral mixture describing the IR data. In the case of the Delta Front, the results were consistent with previous analyses (Dehouck et al., 2022, AGU conf.), but provided more detailed mineralogical identifications. The Yori Pass/Hogwallow Flats, Kaguyak and the lower Rocky Top members share a composition rich in Fe/Mg phyllosilicates (smectite, vermiculite), but also contain Fe/Mg-sulfates, anhydrite and a weak contribution from carbonates (the latter revealed by their 2.3 and 2.5 µm bands). In contrast, IR spectra of the Knife Creek and Devils Tanyard members (which are laterally equivalent) exhibited Fe/Mg phyllosilicates mixed with olivine and pyroxene, and a carbonate fraction, but lacked sulfates. The Amalik interval was unique and mainly marked by the presence of Mg-serpentines, mixed with Fe/Mg-phyllosilicates and Fe/Mg-carbonates. Higher in the stratigraphy, the Upper Fan units were characterized by Fe/Mg-carbonate deposits mixed with phyllosilicates and primary minerals, but no sulfates. This evolution of the spectral facies along the stratigraphy indicates a variation in alteration conditions during the deposition of these strata which are of interest for sampling by Perseverance.