Overview of Perseverance’s Upper Fan Campaign
Résumé
The Mars 2020 Perseverance rover’s mission objective is to collect diverse suites of samples for return to Earth via Mars Sample Return and characterize their geologic and environmental context. Jezero crater was selected as the landing site for Perseverance partially due to the opportunity to explore the western fan deposits, which include water-lain sediments from a diverse ancient watershed that have been lithified and exposed by wind. The Upper Fan Campaign, described here, is the third campaign of the mission; it follows the crater floor campaign and the delta front campaign that explored ~40 m of sedimentary deposits at the base of two lobes of the fan. The Upper Fan Campaign includes the rover traverse from the top of the delta front campaign to the margin unit lining the inner crater rim.
Prior to landing, two major geologic units were identified on the Upper Fan: the truncated curvilinear unit and the blocky unit. Our goals are to characterize the depositional context and major lithologies present in each unit and acquire samples. At time of writing, we have collected two samples and are planning 1-2 more sample acquisitions in the Upper Fan.
The Melyn sample is a fine-grained sandstone from the light toned bands of the truncated curvilinear unit at Tenby, part of the Skrinkle Haven member of the Tenby formation. The sandstone lacks internal structure and decimeter-thick layers have steep (>20°) dip angles. It is interpreted to have formed in subaqueous downslope avalanches, likely on a downstream bar or delta foreset. Melyn contains detrital primary and altered silicates, minor sulfates, and Mg, Fe carbonate grains, coatings, and possible cement.
The Otis_Peak sample is a cross-stratified conglomerate interpreted as part of a higher-energy delta plain braided river deposit in the Carew Castle member of the Tenby formation, overlying the Skrinkle Haven member. Proximity science and remote sensing indicate Otis_Peak contains coarse (up to 4 mm) detrital primary and altered silicates with sulfates and Fe, Mg carbonates.
Perseverance is characterizing the most commonly observed boulder lithologies in the blocky unit, including boulders with dominant olivine and pyroxene spectral signatures. We plan to collect 1-2 more samples in the campaign, including a lithology representative of the latest phase of delta deposition.