¹d’Ischia, M.,¹Manini, P.,²Martins, Z.,³Remusat, L.,⁴O’D. Alexander, C.M.,⁵Puzzarini, C.,⁶Barone, V.,⁷Saladino, R.
Physics of Life Reviews 37, 65-93 Link to Article [DOI: 10.1016/j.plrev.2021.03.002]
¹Department of Chemical Sciences, University of Naples Federico II, Via Cintia 4, Naples, 80126, Italy
²Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, Lisboa, 1049-001, Portugal
³Institut de minéralogie, de physique des matériaux et de cosmochimie, UMR CNRS 7590, Sorbonne Université, Muséum National d’Histoire Naturelle, 61 rue Buffon, Paris, 75005, France
⁴Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road, NW Washington, DC 20015-1305, United States
⁵Department of Chemistry “Giacomo Ciamician”, University of Bologna, Via F. Selmi 2, Bologna, I-40126, Italy
⁶Scuola Normale Superiore, Piazza dei Cavalieri 7, Pisa, I-56126, Italy
⁷Biological and Ecological Sciences Department (DEB), University of Tuscia, Via S. Camillo de Lellis, Viterbo, 01100, Italy

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¹Yang Xiu et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2021.114471]
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
Copyright Elsevier

We report the discovery of indigenous Mn-oxides in Martian regolith breccias Northwest Africa (NWA) 7034 and 7533. These Mn-oxides occur in Mn-rich regions as nanocrystals mixed with silicates, FeOOH, and possible phosphates. The Mn-rich regions contain up to 34 wt% Mn and typically display large chemical gradients on the scale of 10–20 μm. The Martian origin of Mn-oxides was established by the presence of Mn-rich glass (4.8–5.6 wt% Mn) in the fusion crust that crosscuts a Mn-oxides-bearing monzonite clast and by the absence of Mn-oxides on the environmentally exposed surfaces (exterior and fractures) of the meteorites. Manganese K-edge X-ray absorption spectrum (XAS) of the Mn-rich glass in the fusion crust indicated that this glass included high-valent Mn species. Synchrotron micro-X-ray diffraction of a Mn-rich region in a basalt clast and XAS of Mn-rich regions in three monzonite clasts indicate Mn-oxides in these regions are dominantly hollandite-structured with 67–85 mol% of the total Mn being Mn4+. The fact that Mn-rich regions are present in diverse petrological associations but are absent in the matrix of the breccias indicates that the Mn-oxides formed through surface alteration prior to the final brecciation event that assembled NWA 7034 and 7533. Thus, the age of the Mn-oxides is older than the lithification age (arguably 1.35 Ga) of NWA 7034 and 7533. Together with findings of Mn-rich phases within Noachian and Hesperian sedimentary strata in Endeavor and Gale craters, our results suggest that Mn-oxides are a common weathering product on Mars surface, suggesting aqueous environment on the Martian surface with high redox potential.