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Science 30 July 2004:
Vol. 305. no. 5684, pp. 657 - 659
DOI: 10.1126/science.1099397
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Reports

Pinpointing the Source of a Lunar Meteorite: Implications for the Evolution of the Moon

Edwin Gnos,1* Beda A. Hofmann,2 Ali Al-Kathiri,1 Silvio Lorenzetti,3 Otto Eugster,3 Martin J. Whitehouse,4 Igor M. Villa,1 A. J. Timothy Jull,5 Jost Eikenberg,6 Bernhard Spettel,7 Urs Krähenbühl,8 Ian A. Franchi,9 Richard C. Greenwood9

The lunar meteorite Sayh al Uhaymir 169 consists of an impact melt breccia extremely enriched with potassium, rare earth elements, and phosphorus [thorium, 32.7 parts per million (ppm); uranium, 8.6 ppm; potassium oxide, 0.54 weight percent], and adherent regolith. The isotope systematics of the meteorite record four lunar impact events at 3909 ± 13 million years ago (Ma), ~2800 Ma, ~200 Ma, and <0.34 Ma, and collision with Earth sometime after 9.7 ± 1.3 thousand years ago. With these data, we can link the impact-melt breccia to Imbrium and pinpoint the source region of the meteorite to the Lalande impact crater.

1 Institut für Geologie, Universität Bern, Baltzerstrasse 1, CH-3012 Bern, Switzerland.
2 Naturhistorisches Museum der Burgergemeinde Bern, Bernastrasse 15, CH-3005 Bern, Switzerland.
3 Physikalisches Institut, Abteilung für Weltraumforschung und Planetologie, Universität Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland.
4 Laboratory for Isotope Geology, Swedish Museum of Natural History, Box 50007, SE-104 05, Stockholm, Sweden.
5 National Science Foundation–Arizona Accelerator Mass Spectrometry Laboratory, University of Arizona, 1118 East Fourth Street, Tucson, AZ 85721, USA.
6 Paul Scherrer Institut, 5232 Villigen, Switzerland.
7 Max-Planck-Institut für Chemie, Abteilung Kosmochemie, 55020 Mainz, Germany.
8 Departement für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.
9 Planetary and Space Sciences Research Institute, Open University, Milton Keynes MK7 6AA, UK.

* To whom correspondence should be addressed: gnos{at}geo.unibe.ch

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