Retrieving the Properties of Martian Aerosols at Jezero Crater using SuperCam PassiveSky Observations

The SuperCam instrument onboard the Mars2020 Perseverance rover is a suite of remote sensing instruments that is operating on the Martian surface since February 2021 (Maurice et al., 2021 ; Wiens et al., 2021). It notably includes a Visible-InfraRed (VISIR) spectrometer covering the 385–465 nm, 536–853 nm, and 1.3–2.6 μm spectral ranges (Fouchet et al., 2022), which regularly performs observations of the Martian atmosphere using the passive sky geometry (Bertrand et al., 2022). At these wavelengths, scattering by aerosols is strongly sensitive to the particle size. The ability of the passive sky technique to retrieve the atmospheric dust content has been demonstrated in the VIS spectral range with MSL/ChemCam (McConnochie et al., 2018), and SuperCam is now able to probe for the first time the Martian atmosphere from the ground for both the VIS and near-IR domains, which provides further information on the aerosol properties.

Dust and water ice aerosols play an important role in the current Martian climate: they affect the thermal structure of the atmosphere as they absorb and scatter the incoming sunlight, and contribute to the global water cycle of the planet (Haberle et al., 2017). Thus, monitoring the properties of these aerosols is of importance to better understand and model the current Martian climate. On Perseverance, the optical depth of the aerosols above the rover is monitored on a seasonal and local time basis by the MEDA and ZCAM instruments (Toledo et al., 2024 ; Smith et al., 2025 ; Moya-Blanco et al., this conference).

By measuring the spectra of the sky luminosity at two different elevation angles, and by comparing the measurement with the results of a multiple scattering radiative transfer model, we are able to retrieve the aerosol properties for both the dust and water ice. Here we use the DIScrete Ordinate Radiative Transfer (DISORT) code in version 4 (Stamnes et al., 2017) through the pyRT_DISORT (Connour & Wolff, 2024) Python module to retrieve the respective optical depth of dust and water ice from the VISIR passive sky measurements of SuperCam performed since the beginning of the mission in 2021, and constrain their particle size. We assume asymmetric hexahydra dust particles and droxtals shapes for the water ice crystals, and we use vertical atmospheric profile from the Mars Climate Database version 6.1 (Forget et al., 1999 ; Millour et al., 2024). These retrievals complement the ones performed by the rover’s other instruments, notably ZCAM. While it is highly challenging with their measurements to distinguish between dust and water ice contributions in the total optical depth, their results can be directly compared with those from SuperCam, as the wavelength ranges of the two instruments overlap in the visible.