Australia Meteor/Meteorite News- Basaltic Meteorite from Australian Fall 18SEP09

Science 18 September 2009: Vol. 325. no. 5947, pp. 1525 - 1527 DOI: 10.1126/science.1174787

Reports

An Anomalous Basaltic Meteorite from the Innermost Main Belt

Philip A. Bland,^1,* Pavel Spurn,² Martin C. Towner,¹ Alex W. R. Bevan,³ Andrew T. Singleton,⁴ William F. Bottke, Jr.,⁵ Richard C. Greenwood,⁶ Steven R. Chesley,⁷ Lukas Shrben,^1,2 Jiri Borovika,² Zdenek Ceplecha,² Terence P. McClafferty,⁸ David Vaughan,⁹ Gretchen K. Benedix,¹⁰ Geoff Deacon,³ Kieren T. Howard,¹⁰ Ian A. Franchi,⁶ Robert M. Hough¹¹

Triangulated observations of fireballs allow us to determine orbits and fall positions for meteorites. The great majority of basaltic meteorites are derived from the asteroid 4 Vesta. We report on a recent fall that has orbital properties and an oxygen isotope composition that suggest a distinct parent body. Although its orbit was almost entirely contained within Earth’s orbit, modeling indicates that it originated from the innermost main belt. Because the meteorite parent body would likely be classified as a V-type asteroid, V-type precursors for basaltic meteorites unrelated to Vesta may reside in the inner main belt. This starting location is in agreement with predictions of a planetesimal evolution model that postulates the formation of differentiated asteroids in the terrestrial planet region, with surviving fragments concentrated in the innermost main belt.

¹ IARC, Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK.
² Astronomical Institute of the Academy of Sciences, Friova 298, CZ-251 65 Ondejov Observatory, Czech Republic.
³ Department of Earth and Planetary Sciences, Western Australian Museum, Locked Bag 49 Welshpool DC, Western Australia 6986, Australia.
⁴ Space and Atmospheric Physics Group, Department of Physics, Imperial College London, London SW7 2AZ, UK.
⁵ Southwest Research Institute, 1050 Walnut Street, Suite 426, Boulder, CO 80302, USA.
⁶ PSSRI, Open University, Walton Hall, Milton Keynes MK7 6AA, UK.
⁷ Solar System Dynamics Group, Jet Propulsion Laboratory, M/S 301-150, Pasadena, CA 91109, USA.
⁸ Office of Research and Development, Curtin University of Technology, GPO Box U1987, Perth, Western Australia 6845, Australia.
⁹ Post Office Box 187, Nedlands, Perth, Western Australia 6909, Australia.
¹⁰ IARC, Department of Mineralogy, Natural History Museum, London SW7 5BD, UK.
¹¹ CSIRO Exploration and Mining, CRCLEME, ARRC, 26 Dick Perry Avenue, Kensington, Perth, Western Australia 6151, Australia.