ROCK DIVERSITY ON THE FLOOR OF JEZERO CRATER OBSERVED IN MASTCAM-Z MULTISPECTRAL IMAGES FROM THE PERSEVERANCE ROVER

In its first months of exploration in Jezero crater, NASA’s Mars-2020 Perseverance rover has encountered rocks with diverse textures, morphologies, coatings, colors, and spectral properties. Understanding the full variety of these rock characteristics, and mapping their occurrences across the traverse, will be key to interpreting the deposition and modification of the crater floor units. Perseverance has multiple imaging and spectroscopic instruments among its payload; of these, the Mastcam-Z instrument is unique in that it can quickly acquire spectral information over broad spatial areas. Here, we present an overview of the diversity of rock targets observed in Mastcam-Z multispectral observations.

Mastcam-Z is a pair of zoom-lens cameras that provide broadband red/green/blue and narrowband visible to near-infrared color (VNIR, 445-1022 nm), allowing for the acquisition of “spectra” with 14 unique wavelength positions. Mastcam-Z multispectral observations are radiometrically-calibrated to I/F using near-simultaneous observations of its calibration target. For each multispectral observation acquired to date, we extracted representative spectra from regions of interest within the calibrated images and correlated their VNIR spectral properties with rock morphology, surface coatings, and geography across the traverse.

The rock spectra observed by Mastcam-Z are largely controlled by their “redness” in visible wavelengths (consistent with variable dust cover and/or ferric coatings) and by broad absorptions centered near 900-1000 nm or negative slopes in the near-infrared (consistent with varying contributions of pyroxene, olivine, glasses, ferric oxides, smectites and other candidate alteration minerals). The spectral variability of nearfield rocks is not clearly related to rock texture or morphology. To first order, the presence of surficial coatings appears to be the primary influence on VNIR spectral properties, and we document multiple types of surface coatings that are highly variable at small spatial scales. We also observe distinct spectral units corresponding to specific geographic regions on the crater floor. Understanding the relationships between these spectral units, and their geologic context, will be a major focus of the ongoing Mastcam-Z investigation.