Mastcam-Z Spectrophotometric Properties of Materials at the Van Zyl Overlook, Jezero Crater, Mars

Multispectral imaging from the Mars 2020 Perseverance rover provides key constraints on how dust cover and small-scale surface texture influence the photometric behavior of Martian materials. During Sols 63–65, the Mastcam-Z camera acquired multispectral stereo mosaics from Van Zyl Overlook in Jezero crater at five wavelengths between 442 and 1022 nm. These observations span phase angles from near opposition to ~150°, allowing detailed characterization of surface scattering properties across a diverse set of geological units near the landing site.

Radiance and reflectance products were derived using onboard calibration targets. Stereo disparity maps were used to compute incidence, emission, and phase angles at the pixel scale and to incorporate topographic information into the analysis. Regions of interest were selected for seven surface units, including dark and dusty soils, regolith, dust-poor “blue” rocks, dustier “red” rocks, intermediate-toned rocks, and rover wheel tracks. Hapke photometric models employing both one-term and two-term Henyey–Greenstein phase functions were applied to retrieve single-scattering albedo, macroscopic roughness, and phase-function parameters describing the angular distribution of scattered light.

The modeling results show that rocks and soils at Van Zyl Overlook are variably modified by differences in dust coverage and surface texture. Blue rocks are consistently the darkest and most strongly backscattering units across wavelengths, with relatively low single-scattering albedos (w ≈ 0.30–0.40), consistent with minimally dust-coated, rough surfaces. Red rocks are brighter, less backscattering, and exhibit trends toward more forward scattering, particularly at shorter wavelengths, with w values approaching ~0.8 at longer wavelengths. Their photometric behavior, together with their visual appearance, is consistent with relatively thick dust mantles that brighten and smooth the surface at small scales. Intermediate rocks follow the scattering behavior of blue rocks but at slightly higher albedo, suggesting similar substrates with modest additional dust contributions.

Regolith and soils span a continuum of scattering behaviors that broadly track their spectral appearance. Regolith tends to be more backscattering, while red soils show more forward-scattering trends, with blue soils occupying an intermediate regime. Rover wheel tracks represent the most atypical unit: despite relatively flat bidirectional reflectance curves, two-term phase-function solutions indicate backscattering trends. Tracks also exhibit the lowest macroscopic roughness values among all units, consistent with surface compaction and smoothing caused by wheel interaction. This behavior differs from some previous rover track observations, suggesting that wheel-induced modification of porosity or grain arrangement may vary between sites.

Overall, variations in single-scattering albedo, phase-function shape, and macroscopic roughness indicate that dust cover and small-scale surface texture play key roles in controlling photometric differences at Jezero crater. While the observed trends are broadly consistent with early Gale crater results, contrasts with Mars Exploration Rover findings highlight the influence of local surface conditions. Extending similar analyses to additional Mars 2020 and Mars Science Laboratory observations will help further isolate the roles of dust, texture, and physical modification in shaping Martian surface scattering properties.