¹Shounak Dutta, ¹Paul D. Asimow, ¹Kenneth A. Farley, ²Arya Udry, ³Nicholas Randazzo, ⁴Kenneth H. Williford
Journal of Geophysical Research: Planets, 131, e2026JE009746
Link to Article [DOI: 10.1029/2026JE009746]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
²Department of Geoscience, University of Nevada, Las Vegas, NV, USA
³University of Alberta, Edmonton, AB, Canada
⁴Blue Marble Space Institute of Science, Seattle, WA, USA
Published by arrangement with John Wiley & Sons

The Margin Unit, explored by the Mars 2020 Perseverance rover in Jezero crater, is a distinctolivine‐rich lithology whose origin has remained unresolved due to extensive alteration and lack of preservedprimary textures. While hypotheses for its formation range from sedimentary to igneous, recent geochemicaldata allow for quantitative testing of these scenarios. To test the igneous hypothesis, we applied Markov ChainMonte Carlo simulations with MELTS thermodynamic modeling to assess whether the observed olivine andspinel compositions in the Margin Unit are consistent with igneous fractional crystallization. Our simulationsreproduce the observed systematic increase in spinel TiO2/Cr2O3 with decreasing olivine forsterite content, apattern difficult to reconcile with sedimentary mixing processes, providing strong evidence for an igneousorigin for the Margin Unit. Furthermore, continuing evolution of the same magma leads to coexisting olivineand 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. Modeledmagma compositions for the Margin Unit are comparable to the parental melt compositions of the chassignitegroup of Martian meteorites, implying conditions necessary to produce chassignite‐like melts were alreadyestablished early in Noachian Mars