In Situ Radiometric and Exposure Age Dating of the Martian Surface

• Published in: Science (American Association for the Advancement of Science) Vol. 343; no. 6169; p. 389
• Main Authors: Farley, K. A., Malespin, C., Mahaffy, P., Grotzinger, J. P., Vasconcelos, P. M., Milliken, R. E., Malin, M., Edgett, K. S., Pavlov, A. A., Hurowitz, J. A., Grant, J. A., Miller, H. B., Arvidson, R., Beegle, L., Calef, F., Conrad, P. G., Dietrich, W. E., Eigenbrode, J., Gellert, R., Gupta, S., Hamilton, V., Hassler, D. M., Lewis, K. W., McLennan, S. M., Ming, D., Navarro-González, R., Schwenzer, S. P., Steele, A., Stolper, E. M., Sumner, D. Y., Vaniman, D., Vasavada, A., Williford, K., Wimmer-Schweingruber, R. F.
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 24.01.2014; The American Association for the Advancement of Science; American Association for the Advancement of Science (AAAS)
• Subjects: Biomarkers - analysis; Biomarkers - chemistry; Cosmic background radiation; Cosmic Radiation; Cosmic rays; Earth Sciences; Evolution, Planetary; Exobiology; Extraterrestrial Environment - chemistry; Geologic Sediments; Isotopes - analysis; Isotopes - chemistry; Mars; Noble Gases - analysis; Organic Chemicals - analysis; Organic Chemicals - chemistry; Radiation Dosage; Radiometric Dating; RESEARCH ARTICLE ABSTRACTS; Rocks; Sciences of the Universe; Sedimentary rocks; Space exploration; Surface Properties
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.1247166

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.