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The Age of the Carbonates in Martian Meteorite ALH84001

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Science  01 Oct 1999:
Vol. 286, Issue 5437, pp. 90-94
DOI: 10.1126/science.286.5437.90

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Abstract

The age of secondary carbonate mineralization in the martian meteorite ALH84001 was determined to be 3.90 ± 0.04 billion years by rubidium-strontium (Rb-Sr) dating and 4.04 ± 0.10 billion years by lead-lead (Pb-Pb) dating. The Rb-Sr and Pb-Pb isochrons are defined by leachates of a mixture of high-graded carbonate (visually estimated as ∼5 percent), whitlockite (trace), and orthopyroxene (∼95 percent). The carbonate formation age is contemporaneous with a period in martian history when the surface is thought to have had flowing water, but also was undergoing heavy bombardment by meteorites. Therefore, this age does not distinguish between aqueous and impact origins for the carbonates.

  • * Present address: Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131, USA.

  • To whom correspondence should be addressed. E-mail: lborg{at}unm.edu

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