Extensive Lithological Diversity of Float Rocks at the Mount Washburn Mound in Neretva Vallis, Jezero Crater, Mars

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Abstract
During its exploration of Neretva Vallis in Jezero crater, NASA's Mars 2020 Perseverance rover examined Mount Washburn, a set of light‐toned sedimentary mounds that exhibited a diverse array of float rocks. Mastcam‐Z visible/near‐infrared (VISIR) multispectral imaging revealed five spectral types dominated by low‐calcium pyroxene‐bearing rocks, although olivine‐bearing and ferric materials were also identified. SuperCam VISIR point spectroscopy of eight targets noted four spectral groups, including those with low‐Ca pyroxene, hydrated alteration products, and phyllosilicates. SuperCam laser‐induced breakdown spectroscopy data confirmed a wide compositional array among the targets. Overall, these data spanned much of the spectral and compositional range in rocks observed by Perseverance through Sol 1348, with no major outliers, although some rock textures were unique. The rock diversity at Mount Washburn is among the most extensive observed in situ at a single site on Mars, pointing to a multifaceted geological history. Bedrock beneath Mount Washburn exhibited high silica and iron content, closely resembling materials from the nearby Bright Angel sedimentary units and suggesting a possible stratigraphic link. Some geological models of Neretva Vallis are consistent with the idea that Bright Angel‐like materials may have formed the foundation of Mount Washburn, with subsequent deposition of cobbles and boulders as late‐stage fluvial events. These findings suggest that similar rocks—and possibly their source regions—may be encountered during future exploration of the Jezero crater rim and intracrater plains. Such materials would likely sample the olivine/carbonate‐bearing regional units and/or ancient Noachian basement, reflecting the rich geological complexity of the Neretva Vallis watershed.
Funding Information
  • Arizona State University (15‐707/1511125)
  • Jet Propulsion Laboratory (1511125)

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