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Originally published in Science Express on 7 November 2002
Science 29 November 2002:
Vol. 298. no. 5599, pp. 1752 - 1756
DOI: 10.1126/science.1077483
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Research Articles

Martian Meteorite Launch: High-Speed Ejecta from Small Craters

James N. Head,12 H. Jay Melosh,1 Boris A. Ivanov3

We performed high-resolution computer simulations of impacts into homogeneous and layered martian terrain analogs to try to account for the ages and characteristics of the martian meteorite collection found on Earth. We found that craters as small as ~3 kilometers can eject ~107 decimeter-sized fragments from Mars, which is enough to expect those fragments to appear in the terrestrial collection. This minimum crater diameter is at least four times smaller than previous estimates and depends on the physical composition of the target material. Terrain covered by a weak layer such as an impact-generated regolith requires larger, therefore rarer, impacts to eject meteorites. Because older terrain is more likely to be mantled with such material, we estimate that the martian meteorites will be biased toward younger ages, which is consistent with the meteorite collection.

1 Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, USA.
2 Raytheon Missile Systems, Post Office Box 11337, Building 805, M/S L5, Tucson, AZ 85734-1337, USA.
3 Institute for the Dynamics of Geospheres, Russian Academy of Sciences, Moscow, Russia 117939.

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