Alteration of a Mantle‐Derived Dunite Boulder in Jezero Crater, Mars

Abstract

In 2023, the Mars 2020 Perseverance rover explored the youngest preserved deposits on the Western fan of Jezero crater, Mars: a field of meter‐scale boulders dispersed above the previously explored sandstone and siltstone units. Reflectance spectra of the boulders delineated two classes, one olivine‐bearing and one pyroxene‐bearing. A representative boulder from each class was analyzed; here, we present proximity data from the olivine‐rich target, Falcon Lake, revealing a magnesian dunite (Fo ₇₄ ). Such magnesian dunite is distinct from other igneous materials observed in Jezero and consistent with crystallization from a mantle‐derived partial melt. Micron and mm‐scale secondary minerals, identified on the abraded patch of Falcon Lake, include Mg‐serpentine, Fe‐Mg carbonate, and Mg,Fe sulfate. This alteration sequence records sequential precipitation from a single evolving fluid, and the coexistence of disequilibrium sulfate and siderite represents a microscale analog to planet‐wide associations and detections of carbonates and sulfates.