The mineralogical composition of Jezero Crater Western Fan: Multigaussian modeling of Perseverance/SuperCam near-infrared observations and overview of major units

Abstract

The analysis of the mineralogical composition of rocks within the Jezero crater, Mars, enables the reconstruction of the aqueous activity history of the site, formed during the planet’s early epochs. Numerous secondary minerals resulting from aqueous alteration, as well as some primary minerals, are observable through near-infrared reflectance spectroscopy, as performed by the IRS/SuperCam instrument onboard the Perseverance rover. The characterization of these minerals, their distribution within geological units, as well as the composition of their assemblages, is crucial for deciphering the chemical, climatic, and geological history of the Jezero crater. In order to systematically study the growing number of IR spectra collected by the instrument, we have developed an automated method for extracting the characteristics of absorption bands, based on their modeling using a combination of Gaussian curves (MultiGM). The application of this method to the entire IRS dataset reveals a significant diversity of minerals distributed throughout the rover traverse, with a near-systematic presence of phyllosilicates in bedrocks, as well as increasingly frequent occurrences of carbonates on the delta, particularly within the Margin unit. These carbonates exhibit variable 2.5 $\mu$m band positions attributed to different Fe and Mg compositions. The delta front presents the sole unit generally enriched in Fe/Mg sulfates (Yori Pass/Hogwallow Flats) accompanied by occurrences of bassanite (hydrated CaSO₄), whereas the presence of sulfates in other delta units and the crater floor is more sporadic and corresponds to fracture/vesicle fills. Finally, almost all the rocks analyzed with IRS/SuperCam are notably dominated by phyllosilicates signatures (Fe/Mg-smectites, serpentine), excepted for a few outcrops caping the Delta. This phyllosilicate presence witnesses the extended surficial (smectites) and hydrothermal (serpentine) aqueous alteration of Jezero’s rocks, either in situ or carried from the watershed.