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Published August 2015 | Supplemental Material
Journal Article Open

In situ evidence for continental crust on early Mars


Understanding of the geologic evolution of Mars has been greatly improved by recent orbital, in situ and meteorite data, but insights into the earliest period of Martian magmatism (4.1 to 3.7 billion years ago) remain scarce. The landing site of NASA's Curiosity rover, Gale crater, which formed 3.61 billion years ago within older terrain, provides a window into this earliest igneous history. Along its traverse, Curiosity has discovered light-toned rocks that contrast with basaltic samples found in younger regions. Here we present geochemical data and images of 22 specimens analysed by Curiosity that demonstrate that these light-toned materials are feldspar-rich magmatic rocks. The rocks belong to two distinct geochemical types: alkaline compositions containing up to 67 wt% SiO_2 and 14 wt% total alkalis (Na_2O + K_2O) with fine-grained to porphyritic textures on the one hand, and coarser-grained textures consistent with quartz diorite and granodiorite on the other hand. Our analysis reveals unexpected magmatic diversity and the widespread presence of silica- and feldspar-rich materials in the vicinity of the landing site at Gale crater. Combined with the identification of feldspar-rich rocks elsewhere and the low average density of the crust in the Martian southern hemisphere, we conclude that silica-rich magmatic rocks may constitute a significant fraction of ancient Martian crust and may be analogous to the earliest continental crust on Earth.

Additional Information

© 2015 Macmillan Publishers. Received 28 October 2014; accepted 2 June 2015; published online 13 July 2015. The Mars Science Laboratory team is gratefully acknowledged. We would like also to thank D. Baratoux for helpful comments on the manuscript. This research was carried out with financial support from NASA's Mars Exploration Program in the US and in France with the Centre National d'Etudes Spatiales (CNES). Contributions: V.S. conceived the manuscript, analysed data, directed the research and wrote the manuscript; M.J.T. conceived and wrote the manuscript; R.C.W. directed the research, and processed the data; A.C., C.F., O.G., S.M., O.F., J.L., A.O., J.C.B. and P.-Y.M. analysed and processed the data; N.M., S.L.M., L.L.D. M.F. and W.R. contributed to interpretation of the data and prepared the figures; E.M.S. contributed to the interpretation and revision of the manuscript; H.N., D.D., N.L., D.V. and S.C. were involved at various stages in data processing; P.P., P.B. and J.J.W. contributed in providing the orbital and in situ optical spectroscopic context and related state of knowledge in Martian crustal mineralogy. All authors contributed to the writing and revision of the manuscript. Competing financial interests: The authors declare no competing financial interests.

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