WORKSHOP ON EXTRATERRESTRIAL MA_RIALS FROM COLD AND HOT DESERTS P II| July 6-8,1999 Kwa-Maritane, Pilanesberg, South Africa LPI Contribution No. 997 WORKSHOP ON EXTRATERRESTRIAL MATERIALS FROM COLD AND HOT DESERTS July 6-8, 1999 Kwa-Maritane, Pilanesberg, South Africa Edited by Ludolf Schultz, Ian A. Franchi, Arch M. Reid, and Michael E. Zolensky Sponsored by Lunar and Planetary Institute Max-Planck-Institut fur Chemie University of the Witwatersrand Lunar and Planetary Institute 3600 Bay Area Boulevard Houston TX 77058-1113 LPI Contribution No. 997 Compiled in 2000 by LUNAR AND PLANETARY INSTITUTE The Institute is operated by the Universities Space Research Association under Contract No. NASW-4574 with the National Aeronautics and Space Administration. 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LPI Contribution No. 997 iii INTRODUCTION Since 1969 expeditions from Japan, the United States, and European countries have recovered more than 20,000 meteorite specimens from remote ice fields of Antarctica. They represent approximately 4(D0--6(g)0 distinct falls, more than all non-Antarctic meteorite falls and finds combined. Recently many meteorite specimens of a new "population" have become available: meteorites from hot deserts. It turned out that suitable surfaces in hot deserts, like the Sahara in Africa, the Nullarbor Plain in Western and South Australia, or desert high plains of the U.S. (e.g., Roosevelt County, New Mexico), contain relatively high meteorite concentrations. For example, the 1985 Catalogue of Meteorites of the British Museum lists 20 meteorites from Algeria and Libya. Today, 1246 meteorites finds from these two countries have been published in MetBase 4.0. Four workshops in 1982, 1985, 1988, and 1989 have discussed the connections between Antarctic glaciology and Antarctic meteorites, and the differences between Antarctic meteorites and modem falls. In 1995, a workshop addressed differences between meteorites from Antarctica, hot deserts, and modern falls, and the implications of possible different parent populations, infall rates, and weathering processes. Since 1995 many more meteorites have been recovered from new areas of Antarctica and hot deserts around the world. Among these finds are several unusual and interesting specimens like lunar meteorites or SNCs of probable martian origin. The Annual Meeting of the Meteoritical Society took place in 1999 in Johannesburg, South Africa. As most of the recent desert finds originate from the Sahara, a special workshop was planned prior to this meeting in Africa. Topics discussed included micrometeorites, which have been collected in polar regions as well as directly in the upper atmosphere. The title "Workshop on Extraterrestrial Materials from Cold and Hot Deserts" was chosen and the following points were emphasized: (1) weathering processes, (2) terrestrial ages, (3) investigations of "unusual" meteorites, and (4) collection and curation. Fig. 1. Meteorite finds in the Sahara. Cluster in Algeria belongs to Fig. 2. Meteorite finds of the USA show a cluster in dry areas the Acfer and Tanesrouf finds, those in Libya to Hammadah al of Texas and New Mexico. Hamra and Dar al Gani. Fig. 3. Numerous meteorite finds show up at the Nullarbor desert in Fig. 4. The many Antarctic meteorites are found on Blue Australia. lcefieids located along the Transantarctic Mountains and at the Yamato Mountains. 2 2 2_ LPI Contribution No. 997 v CONTENTS Program ................................................................................................................................................. ix Summary of Previous Workshop ......................................................................................................... 1 Workshop Summary ............................................................................................................................. 3 Collections, Collecting Areas, and Pairing Problems ................................................................. 3 Weathering Effects ...................................................................................................................... 4 Terrestrial Age Determinations ................................................................................................... 5 Interplanetary Dust Particles .................................................................................................... ,.. 5 Noble Gases and Cosmic-Ray Effects ........................................................................................ 6 Repositories of Desert Meteorites ........................................................................................................ 7 Acknowledgments ........................... ;...................................................................................................... 9 Abstracts .............................................................................................................................................. 11 The Natural Thermoluminescence Survey of Antarctic Meteorites: Ordinary Chondrites at the Grosvenor Mountains, MacAlpine Hills, Pecora Escarpment and Queen Alexandra Range, and New Data for Elephant Moraine Ice Fields P. H. Benoit and D. W. G. Sears ................................................................................... 11 Meteorites from the Nullarbor, Australia: An Update A. W. R. Bevan, P. A. Bland, and A. J. T. Jull ............................................................... 15 Ice Flow as the Principal Sink for Antarctic Meteorites P. A. Bland, A. J. T. JulI, A. W. R. Bevan, T. B. Smith, F. J. Berry, and C. T. PiIlinger ......................................................................................................... 17 Pairing among EET87503 Group Howardites and Polymict Eucrites P. C. Buchanan, D. J. Lindstrom, and D. W. MittIefehldt. ............................................ 21 Chemical Alteration of Hot Desert Meteorites: The Case of Shergottite Dar al Gani 476 G. Crozaz and M. Wadhwa ........................................................................................... 25 vi Deserts II Workshop Chemical Compositions of Large Interplanetary Dust Particles from the Stratosphere and Small Antarctic Micrometeorites: Evidence for Element Loss and Addition in the Antarctic Micrometeorites G. J. Flynn, S. R. Sutton, and W. Klrck ......................................................................... 28 The Influence of Terrestrial Weathering on Implanted Solar Gases in Lunar Meteorites I. Franchi, A. B. Verchovslcy, and C. T. Pillinger ......................................................... 33 Meteorites from Cold and Hot Deserts: How Many, How Big, and What Sort M. M. Grad)'. ................................................................................................................. 36 Using 14C and 14C-_°Be for Terrestrial Ages of Desert Meteorites J. T. JuIl, P. A. Bland, S. E. Klandrud, L. R. McHargue, A. W. R. Bevan, D. A. Kring, and F. Wlotzka .......................................................................................... 41 The Gold Basin Strewn Field, Mojave Desert, and its Survival from the Late Pleistocene to the Present D. A. Kring, A. J. T. JuIl, and P. A. Bland .................................................................... 44 Thermally Mobile Trace Elements in Carbonaceous Chondrites from Cold and Hot Deserts M. E. Lipschutz .............................................................................................................. 46 Historical Notes on Three Exceptional Meteorites of Southern Africa: The Cape of Good Hope, Gibeon, and Hoba U. B. Marvin .................................................................................................................. 48 Saharan Meteorites with Short or Complex Exposure Ages S. MercheI, M. Altmaier, T. Faestermann, U. Herpers, K. Knie, G. Korschinek, P. W. Kubik, S. Neumann, R. Michel, and M. Suter ...................................................... 53 Cosmogenic and Trapped Gas Components in the Martian Meteorite Dar al Gani 476 from Hot Desert ...... S. V. S. Murty and R. K. Mohapatra .................................... ............................. 'i ........... 57 Thermal Effects on Mineralogy, Noble Gas Composition, and Carbonaceous Material in CM Chondrites T. Nakamura, T. Kitajima, and N. Takaoka ................................................................... 61 TerreStrial Ages of Antarctic Meteorites Up Date 1999 .... K. Nishiizumi, M. W. Caffee, and K. C. WeIten ................................................... ......,._ 64 Type I Cosmic Spheres: Key to a Major but Poorly Sampled Asteroid Population? L. E. Nyquist .................................................................................................................. 65 LPI Contribution