A Shared Magma Source for the Olivine‐Rich Units in Jezero Crater, Mars

The Margin Unit, explored by the Mars 2020 Perseverance rover in Jezero crater, is a distinct olivine‐rich lithology whose origin has remained unresolved due to extensive alteration and lack of preserved primary textures. While hypotheses for its formation range from sedimentary to igneous, recent geochemical data allow for quantitative testing of these scenarios. To test the igneous hypothesis, we applied Markov Chain Monte Carlo simulations with MELTS thermodynamic modeling to assess whether the observed olivine and spinel compositions in the Margin Unit are consistent with igneous fractional crystallization. Our simulations reproduce the observed systematic increase in spinel TiO 2 /Cr 2 O 3 with decreasing olivine forsterite content, a pattern difficult to reconcile with sedimentary mixing processes, providing strong evidence for an igneous origin for the Margin Unit. Furthermore, continuing evolution of the same magma leads to coexisting olivine and clinopyroxene compositions that suggest a genetic link between the Margin Unit and the crater floor olivine‐rich unit, Séítah, pointing toward the existence of an extensive igneous complex within Jezero crater. Modeled magma compositions for the Margin Unit are comparable to the parental melt compositions of the chassignite group of Martian meteorites, implying conditions necessary to produce chassignite‐like melts were already established early in Noachian Mars.