In situ radiometric and exposure age dating of the martian surface.


We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray-produced (3)He, (21)Ne, and (36)Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.

DOI: 10.1126/science.1247166

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@article{Farley2014InSR, title={In situ radiometric and exposure age dating of the martian surface.}, author={Kenneth A. Farley and Charles A Malespin and Paul R. Mahaffy and John P. Grotzinger and Paulo M Vasconcelos and Ralph E. Milliken and Michael C. Malin and Kenneth S Edgett and Alexander A. Pavlov and J A Hurowitz and J A Grant and Hugh B Miller and Raymond E. Arvidson and Luther W. Beegle and Fred Calef and Pamela G. Conrad and William Eric Dietrich and J L Eigenbrode and Ralf Gellert and Sunil Kumar Gupta and Victoria E . Hamilton and Donald M. Hassler and Kevin W. Lewis and S M McLennan and D W Ming and Rafael Navarro-Gonzalez and Susanne P. Schwenzer and A . K . Steele and Edward M. Stolper and Dawn Y. Sumner and David T. Vaniman and A R Vasavada and Kenneth H Williford and Robert F. Wimmer-Schweingruber}, journal={Science}, year={2014}, volume={343 6169}, pages={1247166} }