Early observations from the Perseverance rover suggested a deltaic origin for the western fan of Jezero crater only from images of the Kodiak butte. Here, we use images from the SuperCam Remote Micro-Imager and the Mastcam-Z camera to analyze the western fan front along the rover traverse, and further assess its depositional origin. Outcrops in the middle to lower half of hillslopes are composed of planar, inclined beds of sandstone that are interpreted as foresets of deltaic deposits. Foresets are locally structured in ~20-25 m thick, ~80-100 m long, antiformal structures interpreted as deltaic mouth bars. Above these foresets are observed interbedded sandstones and boulder conglomerates, interpreted as fluvial topset beds. One well-preserved lens of boulder conglomerate displays rounded clasts within well-sorted sediment deposited in fining upward beds. We interpret these deposits as resulting from lateral accretion within fluvial channels. Estimations of peak discharge rates give a range between ~100 and ~500 m3.s-1 consistent with moderate to high floods. By contrast, boulder conglomerates exposed in the uppermost part of hillslopes are poorly sorted and truncate underlying beds. The presence of these boulder deposits suggests that intense, sediment-laden flood episodes occurred after the deltaic foreset and topset beds were deposited, although the origin, timing, and relationship of these boulder deposits to the ancient lake that once filled Jezero crater remains undetermined. Overall, these observations confirm the deltaic nature of the fan front, and suggest a highly variable fluvial input.

Through rover missions and martian meteorites received on Earth, the surface of Mars has showed unexpectedly elevated concentrations of transition metals usually measured in minor and trace concentrations in silicate rocks compared to the average crust. Gale crater presents one of the most diverse geological records in terms of its complex fluid and magmatic history described through the sedimentary and igneous records, respectively. Transition metals, such as Mn, Co, Ni, Cu, and Zn, are highly concentrated within various sedimentary rocks and diagenetic features, suggesting their mobilization through fluid circulation. This paper presents the first compilation of elevated concentrations of transition metals measured by the Curiosity rover and reviews the origin of such metals in Gale crater, highlighting the existence of a hydrothermal or magmatic-hydrothermal deposit in its vicinity. The discovery of felsic magmatism on Mars opens up to novel perspectives in terms of the type of metal deposits that current and future exploration could evidence at the surface of Mars and raise questions about the global abundance of such metals. Constraining the abundance of transition metals is also a central question for exobiology purposes. Because on Earth living organisms use transition metals for their survival and functioning, should live have arisen on Mars, the availability of such chemical elements at the surface could have been essential for its development. An accurate assessment of in situ metal resources and potential risks for health will be key for the preparation of human exploration of Mars as recently announced by NASA.