title: In situ radiometric and exposure age dating of the martian surface.
abstract: 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.
authors: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
authors: K A
authors: KA
authors: Farley
authors: C
authors: C
authors: Malespin
authors: P
authors: P
authors: Mahaffy
authors: J P
authors: JP
authors: Grotzinger
authors: P M
authors: PM
authors: Vasconcelos
authors: R E
authors: RE
authors: Milliken
authors: M
authors: M
authors: Malin
authors: K S
authors: KS
authors: Edgett
authors: A A
authors: AA
authors: Pavlov
authors: J A
authors: JA
authors: Hurowitz
authors: J A
authors: JA
authors: Grant
authors: H B
authors: HB
authors: Miller
authors: R
authors: R
authors: Arvidson
authors: L
authors: L
authors: Beegle
authors: F
authors: F
authors: Calef
authors: P G
authors: PG
authors: Conrad
authors: W E
authors: WE
authors: Dietrich
authors: J
authors: J
authors: Eigenbrode
authors: R
authors: R
authors: Gellert
authors: S
authors: S
authors: Gupta
authors: V
authors: V
authors: Hamilton
authors: D M
authors: DM
authors: Hassler
authors: K W
authors: KW
authors: Lewis
authors: S M
authors: SM
authors: McLennan
authors: D
authors: D
authors: Ming
authors: R
authors: R
authors: Navarro-González
authors: S P
authors: SP
authors: Schwenzer
authors: A
authors: A
authors: Steele
authors: E M
authors: EM
authors: Stolper
authors: D Y
authors: DY
authors: Sumner
authors: D
authors: D
authors: Vaniman
authors: A
authors: A
authors: Vasavada
authors: K
authors: K
authors: Williford
authors: R F
authors: RF
authors: Wimmer-Schweingruber
mesh_terms: D015415:Biomarkers / Q000032:analysis / Q000737:chemistry; D003359:Cosmic Radiation; D019419:Evolution, Planetary; D018559:Exobiology; D005118:Extraterrestrial Environment / Q000737:chemistry*; D019015:Geologic Sediments; D007554:Isotopes / Q000032:analysis / Q000737:chemistry; D018535:Mars; D005741:Noble Gases / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis / Q000737:chemistry; D011829:Radiation Dosage; D055110:Radiometric Dating; D013499:Surface Properties
chemical_list: D015415:Biomarkers; D007554:Isotopes; D005741:Noble Gases; D009930:Organic Chemicals