Geological Characterisation of Oxia Planum Analogues using ExoMars Rosalind Franklin Instrument Emulators

The ExoMars Rosalind Franklin Rover, set to launch in 2028, is equipped with a payload of instruments designed to facilitate the search for signs of ancient microbial life at the Martian surface and sub-surface to a depth of 2 m [1]. The landing site, Oxia Planum, has been selected based on engineering and science requirements and its unique geological setting, which consists of clay-rich deposits capped by a unit that may have shielded potential biosignatures from degradation due to cosmic ray bombardment and oxidation at the Martian surface. The site exhibits remote-sensing evidence for periodically available liquid water in the Noachian era (i.e. a high likelihood of habitability) and a phyllosilicate-bearing clay unit which could retain organic matter within its structure (i.e. high biosignature preservation potential), making it a compelling location for the detection of potential Martian biosignatures [2]. 

The Panoramic Camera (PanCam) instrument on board Rosalind Franklin is equipped with two wide-angle cameras (WACs) and a high-resolution camera (HRC) designed to perform geological characterisation of the landing site and aid in target selection for further analysis. The WACs provide stereographic multispectral images of science targets with 11 geological filters, encompassing a spectral range of 440–1000 nm [3], and will be used in tandem with Enfys, a linear variable filter spectrometer with spectral range of 0.9–2.5 µm, to perform geochemical analysis on outcrops to determine their suitability as drill target locations [4]. The Close-Up Imager (CLUPI) instrument [5] provides complementary high-resolution imagery of science targets, revealing texture, colour and rock structure to aid in their geological characterisation. Together, these instruments are vital for detecting the presence of any potential biosignatures and ensuring that the limited sub-surface samples collected during the mission are of high scientific quality.  

Rover resources during the mission are limited, and plans must have some level of reactivity on a sol-to-sol basis to account for our evolving understanding of the landing site. To facilitate cross-instrumental analysis between HRC, the WACs, CLUPI and Enfys-representative spectrometer data, a library of mission-representative data products of Oxia Planum analogues will be collected. This library, obtained using nominal operational recommendations under a controlled environment, simulates a single rover operational cycle as would be performed during the mission, highlighting the optimal observational conditions for geological features of interest across a range of scales. Operational recommendations for the instruments will be derived from this database, highlighting areas of instrument overlap (both scientific and geometric) or particularly complementary data collection procedures (such as assessing the gain in data type and diversity that contributes to geological interpretation between WAC and HRC observations on a single target).  

10 samples—including clay-rich, biosignature-bearing samples, samples containing hydrated silica, samples displaying ‘reduction spots’, and potential target contaminants e.g. dust simulants—have been curated for data collection across the PanCam and CLUPI instruments. These samples have been selected based on prior analysis of CRISM and OMEGA data at Oxia Planum, amongst others, in numerous studies [2] [6] [7], with some samples selected due to similarities to small-scale features that would not be discernible at remote sensing scales (e.g. samples selected based on the potential detection of redox-driven mineral associations in Jezero crater [8]). Samples have been analysed using the PanCam training model (TM), with future planned analysis using the CLUPI enhanced engineering model (EM+), producing a reference library of mission-representative data products across varying operationalparameters (e.g. observation distance and angle, illumination conditions, and exposure time).  

This study acts as a cross-instrumental, data driven approach to quantifying instrument contribution to overall data downlink on a given target to optimise data return and inform future operations cycles, and is complementary to ongoing work on cross-instrumental geological characterisation across the ExoMars SOWG. 

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