https://ntrs.nasa.gov/search.jsp?R=19960027473 2020-06-16T04:02:37+00:00Z NASA-CR-200512 WORKSHOP ON METEORITES FROM COLD AND HOT DESERTS LPI Technical Report Number 95-02 Lunar and Planetary Institute 3600 Bay Area Boulevard Houston TX 77058-1113 LPI/TR--95-02 WORKSHOP ON METEORITES FROM COLD AND HOT DESERTS Edited by Ludolf Schultz, John O. Annexstad, and Michael E. Zolensky Held at N6rdlingen, Germany July 20-22, 1994 Sponsored by Lunar and Planetary Institute Max-Planck-Institut fiir Chemie Rieskratermuseum N6rdlingen Lunar and Planetary Institute 3600 Bay Area Boulevard Houston "IX 7705_;- 11 i 3 LPI Technical Report Number 95-02 LPI/TR--95-02 Compiled in 1995 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. Material in this volume may be copied without restraint for library, abstract service, education, or personal research purposes; however, republication of any paper or portion thereof requires the written permission of the authors as well as the appropriate acknowledgment of this publication. This report may be cited as Schultz L., Annexstad _. O., and Zolensky M. E., eds. (1995) Workshop on Meteoritesfrorn Cold and Hot Deserts. LPI Tech. Rpt. 95-02, Lunar and Planetary Institute, Houston. 83 pp. This report is distributed by ORDER DEPARTMENT Lunar and Planetary Institute 3600 Bay Area Boulevard Houston TX 77058-1113 Mail order requestors will be invoiced for the cost of shipping and handling. LPI Technical Report 95-02 iii Introduction Until 1969 only four meteorites had been found in the cold desert of Antarctica. Since that year, however, expeditions from Japan, the United States, and various European countries have recovered more than 16,000 meteorite specimens from remote ice fields. They represent approximately 3000-5000 distinct falls, more than all non-Antarctic meteorite falls and finds combined. Four previous workshops have discussed the connection between Antarc- tic glaciology and Antarctic meteorites, their stranding surfaces, and differ- ences between Antarctic and non-Antarctic meteorites. The cause of the differences among these groups is still under discussion. Two different lines have been explored: These differences have an extraterrestrial cause, or they are the result of secondary effects on Earth. 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 Austra- lia, or desert high plains of the U.S. (Roosevelt County), contain relatively high meteorite concentrations. For example, the 1985 Catalog of Meteorites of the British Museum lists 20 meteorites from Algeria and Libya. Ten years later, 543 meteorites finds from these two countries have been published in the Catalog and Meteoritical Bulletins. Among Antarctic meteorites and those from hot deserts, several unusual and interesting specimens have been found. While the mean terrestrial age of Antarctic meteorites is of the order of 105 yr, that of meteorites from hot deserts is about 1 order of magnitude less. In spite of this age difference, weathering effects are more pronounced in the latter group. Thus, meteorites from hot deserts form another group that differs from Antarctic finds and modern falls with respect to terrestrial ages and the influence of the terrestrial environment on these rocks. The idea to hold a workshop in which participants could discuss meteorite finds from cold and hot deserts was born in a EUROMET business meeting in 1992. EUROMET is a collaboration of over 50 European laboratories in 12 countries. Its purpose is to foster the collection, distribution, and interdis- ciplinary investigation of new meteorites and cosmic dust. EUROMET has accumulated over 1000 meteorite specimens in a series of expeditions to Antarctica and hot deserts. The current workshop was organized to address the following points: (1) definition of differences between meteorites from Antarctica, hot deserts, and modern falls; (2) discussion of the causes of these differences; (3) impli- cations of possible different parent populations, infall rates, weathering processes, etc.; (4) collection, curation, and distribution of meteorites; and (5) planning and coordination of future meteorite searches. iv Workshop on Meteorites from Cold and Hot Deserts A first announcement of the planned workshop on "Meteorites from Cold and Hot Deserts" was mailed in fall 1993, and resulted in about 80 responses, which led to its definite planning. The workshop was held July 20-22, 1994, in N6rdlingen, Germany, on the floor of the meteorite impact crater N6rd- linger Ries, which was formed about 15 m.y. ago. The meeting was attended by 59 participants from 11 countries. In all, 32 papers were presented, and toward the end of the workshop several parties discussed their future plans to collect meteorites in hot deserts and in Antarctica. The last day of the work- shop was devoted to a field trip to several outcrops of the N6rdlinger Ries impact crater. Following the workshop program, which appears in this volume, we provide summaries of the workshop presentations and discussions. General Workshop Recommendations As meteorite searches continue year after year, a mounting body of evidence about concentrations and physical parameters is gained. It seems, however, that a picture of what precisely is involved in each case or site is an elusive quantity. This workshop, above all, has pointed out the complexity of the situation and the need for more searches, more meteorites, and more investigations. The conveners and most participants agreed that researchers and search- ers should meet at least every three to four years to exchange ideas and to refine mechanisms. The workshop format prior to an annual Meteoritical Society meeting seems to be a workable vehicle. LPI Technical Report 95-02 v Acknowledgments We thank all participants of the workshop who contributed valuable research papers and participated in discussions. In the course of the preparation for the workshop, as well as during the meeting, able assistance was received from L. Franke (Mainz) and H. Stangel (N6rdlingen). We want to thank all sponsoring agencies, especially the Lunar and Planetary Institute, Houston, the Rieskratermuseum N6rdlingen and its friends, the town of N6rdlingen, the Verein Rieser Kulturtage, and the Max-Planck-Institut fiir Chemie, Mainz, for technical, logistical, and financial help. LPI Technical Report 95-02 vii Program Wednesday, July 20, 1994 1200-1330 Registration 1330-1345 Welcome 1345-1545 METEORITE SEARCHES Chair: M.M. Grady R. P. Harvey Current Research Activities of ANSMET: Recent Studies in the Walcott N_vd Region L° Folco, I. A. Franchi, M. Mellini, and C. T. Pillinger 1993/94 Antarctic Field Season: A Report on Activities Undertaken by the EUROMET/PNRA Meteorite Collection Expedition to Frontier Mountain, North Victoria Land A. M. Reid, P. Jake_, M. E. Zolensky, and R. McG. Miller Recovery of Three Ordinary Chondrites from the Namib Desert, Western Namibia I° A. Franchi, G. Delisle, and C. T. Pillinger An Evaluation of the Meteorite Potential of the Jiddat AI Harasis and the Rub Al Khali Regions of Southern Arabia M. E. Zolensky, J. W. Schutt, A. M. Reid, P. Jake[, E. Martinez de los Rios, and R. M. Miller Locating New Meteorite Recovery Areas O. Gerel, A. Bischoff, L. Schultz, J. Schltiter, L. Baljinnyam, D. Borchuluun, C. Byambaa, and D. Garamjav The 1993 EUROMET/Mongolian Expedition to the Gobi Desert: Search for Meteorites 1615-1715 MECHANISMS AND CHALLENGES Chair: J.O. Annexstad G. Delisle Storage of Meteorites in Antarctic Ice During Glacial and Interglacial Stages R. P. Harvey Moving Targets: The Effect of Supply, Wind Movement, and Search Losses on Antarctic Meteorite Size Distributions viii Workshop on Meteorites from Cold and Hot Deserts I. P. Wright, M. M. Grady, and C. T. Pillinger The Acquisition of Martian Sedimentary Rocks: For the Time Being, Collection of Meteorites from Terrestrial Desert Areas Represents the Best Hope 1730-1830 Visit to the Rieskrater Museum 1900 Reception by the Mayor of N6rdlingen at the Rathaus Thursday, July 21, 1994 0830-0910 COLLECTIONS Chair: R.S. Clarke M. M. Lindstrom and R. Score Populations, Pairing, and Rare Meteorites in the U.S. Antarctic Meteorite Collection T. Geiger and A. Bischoff Meteorite Find Locations, Shock Classification, and Pairing of 464 Meteorites from the Sahara, and the Mineralogical and Chemical Classification of Rare Types 0910-1120 WEATHERING EFFECTS Chair: M.E. Zolensky R. D. Ash and C. T. Pillinger The Fate of Meteoritic Carbon in Hot and Cold Deserts P. Bland, F. J. Berry, and C. T. PiUinger Iron-57 M6ssbauer Spectroscopy Studies of Weathering in Ordinary Chondrites from Roosevelt County, New Mexico G. Crozaz Pyroxene, the Indicator of Pervasive Trace-Element Mobilization in Antarctic Meteorites U. Kr/ihenbtihl and M. Langenauer Comparison of the Distribution of Halogens in Chondrites from Antarctica and from Western Australia J. Newton, M. A. Sephton, and C. T. Pillinger Contamination Differences Between C03 Falls and Antarctic and Saharan Finds: A Carbon and Nitrogen Study LPI Technical Report 95-02 ix P. Scherer, L. Schultz, and Th. Loeken Weathering and Atmospheric Noble Gases in Chondrites from Hot Deserts 1120-1230 COSMOGENIC NUCLIDES Chair: D.W.G. Sears M. Knauer, U. Neupert, R. Michel, G. Bonani, B. Dittrich-Hannen, I. Hajdas, S. Ivy, P. W. Kubik, and M. Suter Measurement of the Long-Lived Radionuclides Beryllium-l O, Carbon-14, Aluminum-26 in Meteorites from Hot and Cold Deserts by Accelerator Mass Spectrometry (AMS) B. Meltzow, U. Herpers, W. Klas, B. Dittrich-Hannen, P. W. Kubik, and M. Suter Beryllium-l O and Aluminum-26 Concentration in Carbonaceous Chondrites and Other Meteorite Types from the Sahara K. C. Welten, L. Lindner, and K. van der Borg Cosmogenic Beryllium-lO and Aluminum-26 in Lewis Cliff Meteorites R.