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Petrological evidence for shock melting of carbonates in the martian meteorite ALH84001

Nature volume 387, pages 377–379 (1997)Cite this article

Abstract

The meteorite ALH84001—a shocked igneous rock of probable martian origin—contains chemically and isotopically heterogeneous carbonate globules1–8, associated with which are organic and inorganic structures that have been interpreted7 as possible fossil remains of ancient martian biota. A critical assumption underlying this suggestion is that the carbonates formed from low-temperature fluids penetrating the cracks and voids of the host rock3. Here we report petrological studies of ALH84001 which investigate the effects of shock on the various mineralogical components of the rock. We find that carbonate, plagioclase and silica were melted and partly redistributed by the same shock event responsible for the intense local crushing1,2 of pyroxene in the meteorite. Texture and compositional data show that, during the period of shock decompression, monomineralic melts were injected into pyroxene fractures that were subsequently cooled and resealed within seconds. Our results therefore suggest that the carbonates in ALH84001 could not have formed at low temperatures, but instead crystallized from shock-melted material; this conclusion weakens significantly the arguments that these carbonates could host the fossilized remnants of biogenic activity.

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Authors and Affiliations

  1. Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, 96822, USA

    Edward R. D. Scott, Akira Yamaguchi & Alexander N. Krot

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  1. Edward R. D. Scott
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  2. Akira Yamaguchi
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  3. Alexander N. Krot
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Scott, E., Yamaguchi, A. & Krot, A. Petrological evidence for shock melting of carbonates in the martian meteorite ALH84001. Nature 387, 377–379 (1997). https://doi.org/10.1038/387377a0

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