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Recent Meteorite Recoveries in Michigan
Returned samples of solar-system materials are of the highest scientific value because they are known to come from bodies for which other kinds of information are available to complement studies of the samples in terrestrial laboratories. However, only a few solar-system bodies other than Earth have been sampled by human or robotic missions. Lunar rocks returned by Apollo and Luna missions, comet dust returned from comet 81P/Wild 2 by NASA’s Stardust mission, and mineral grains from the regolith of asteroid 25143 Itokawa recently returned by the Hayabusa mission, sample only a few specific solarsystem bodies (the Moon, one comet, and one asteroid).
Meteorites are naturally delivered samples that are our only direct samples from a large a variety of parent bodies throughout the solar system. In their chemical compositions, minerals, and textures they preserve direct evidence of the processes by which our solar system’s planets and small bodies originated, were modified, and evolved to their present state.
At the broadest level of compositional classification, meteorites include objects that consist mainly of metal (irons), predominantly of silicate minerals (stones or stony meteorites), and subequal abundances of metal and silicates (stony irons). Stony meteorites are subdivided into those with textural evidence of familiar (to geologists) igneous differentiation processing on their parent bodies, and those containing textural evidence of cooling and solidification of individual grains from vapor and melted dust followed by assembly of the solids into rocks and parent bodies that did not differentiate to produce magmas and igneous rocks. The defining features of the latter group are chondrules, generally spherical mm to sub-mm-sized silicate-dominated solids that are solidified droplets formed by flash heating and rapid cooling of precursor solids in the early solar nebula. Stony meteorites containing chondrules, and closely related meteorites in which evidence of chondrules may have been destroyed during the meteorite’s history, are called chondrites. Stony meteorites with igneous textures lack chondrules and are called achondrites. Meteorites from large, differentiated parent bodies (e.g. Mars, the Moon, differentiated Main Belt asteroids) complement scientific understanding of those parent bodies arrived at by other means, including ground-based astronomical observations and orbital and landed missions. Undifferentiated meteorites are important sources of information about primitive asteroids.
The natural delivery process involves ejection of a meteoroid from its parent body, interplanetary transit, dramatic passage through Earth’s atmosphere, and arrival at Earth’s surface as a meteorite. Freshly fallen meteorites, recovered promptly after their witnessed fall, are referred to as ‘falls.’ Most meteorites available for scientific study are referred to as ‘finds,’ recovered after unwitnessed arrival and some exposure to the terrestrial surface environment, often over millennial or longer timescales. Meteorites are named for major geographic features near their recovery site.
Michigan’s meteorites are typical of meteorites recovered around the world. Irons are the most easily recognized among finds; all Michigan finds are irons. Stony meteorites are best recognized when their fall is witnessed; all Michigan stony meteorites are falls. All documented Michigan stony meteorites are ordinary chondrites, the most common variety among falls.
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MICHAEL ANTHONY VELBEL (Ph.D., Yale University, 1984) is Professor of Geological Sciences at Michigan State University, East Lansing, MI. He studies regolith geoscience, and the rates and mechanisms of mineral-water interactions during rock and mineral weathering, emphasizing the geological, mineralogical, geochemical, and geomorphic factors which control mineral alterations at the Earth's surface and the migration of chemical elements through the landscape; and small-watershed geochemistry. Related areas of research include terrestrial weathering of Antarctic meteorites; rock-, mineral-, and chemical-weathering on Mars and in Martian meteorites; pre-terrestrial aqueous alteration on other meteorite parent bodies; and preservation of sample integrity for future sample-return missions. He was a member of the Mineralogy-Petrology subteam of the NASA Stardust mission Preliminary Examination Team (2006). In addition to MSU, Prof. Velbel has held visiting appointments at the University of Cincinnati, the Université Paul Cézanne (Université d'Aix-Marseilles III), and the Australian National University, and held NASA/ASEE Summer Faculty Fellowships at the NASA Johnson Space Center in 1987 and 1999.
MICHAEL ANTHONY VELBEL, Professor of Geological Sciences, Michigan State University, East Lansing, MI 48824-1115 (517) 355-4626
Education:
Ph.D., 1984 Yale University (Geology/Geochemistry)
B.A., 1978 Northwestern University (Geological Sciences)
Academic Appointments:
Chair, Department of Geological Sciences, Michigan State University, 1999-present
NASA/ASEE Summer Faculty Fellow, NASA Johnson Space Center, 1999
Visiting Fellow, Department of Geology and Cooperative Research Centre for Landscape Evolution and Mineral Exploration, Australian National University, Jan.-April, 1998.
Professor of Geological Sciences, Michigan State University, 1993-present.
Visiting Associate Professor of Geology, Faculté des Sciences-St Jérôme, Université Paul Cézanne (formerly d'Aix-Marseilles III), April, 1992.
Visiting Associate Prof. of Geology, University of Cincinnati, 1990-1991.
Assoc. Prof., Geological Sciences, Michigan State University, 1988-1993.
NASA/ASEE Summer Faculty Fellow, NASA Johnson Space Center, 1987
Asst. Prof., Geological Sciences, Michigan State University, 1983-1988.
Five publications most relevant to proposed research
Velbel, M.A., 1999. Bond strength and the relative weathering rates of simple orthosilicates. American Journal of Science, v. 299, p. 679-696.
Velbel, M.A., 1999. Rate and duration of aqueous alteration on the carbonaceous chondrite parent body:
Petrographic studies of kinetically controlled olivine replacement textures. NASA Contractor Report, pp. 19-1 to 19-15.
Velbel, M.A., Basso, C.L., Jr., and Zieg, M.J., 1996. The natural weathering of staurolite: Crystal-surface textures, relative stability, and the rate-determining step. American Journal of Science, v. 296, p. 453-472.
Velbel, M.A., 1993. Formation of protective surface layers during silicate-mineral weathering under well-leached, oxidizing conditions. American Mineralogist 78:408-417.
Velbel, M.A., 1989. Weathering of hornblende to ferruginous products by a dissolution-reprecipitation mechanism: Petrography and stoichiometry. Clays and Clay Minerals 37:515-524.
Five other significant research publications
Velbel, M.A., 1998. Geochemical Kinetics of Mineral-Water Interactions: Chemical Reaction Rates and Rate Processes in Mineral and Rock Weathering. Short Course Notes, Cooperative Research Centre for Landscape Evolution and Mineral Exploration, Canberra, ACT, Australia, 6-9 April 1998, 66 pp. Osborn, W., Matty, D., Velbel, M., Brown, P., and Wacker, J., 1997. Fall and recovery of the Coleman chondrite and its associated fireball. Meteoritics & Planetary Science, v. 32, p. 781-790.
Velbel, M.A., 1996. Some effects of clay minerals on the kinetics of silicate-mineral weathering. Short papers from the Fourth International Symposium on the Geochemistry of the Earth's Surface (S. H. Bottrell, ed.), Department of Earth Sciences, University of Leeds, pp. 520-524.
Velbel, M.A., 1993. Temperature dependence of silicate weathering in nature: How strong a negative feedback on long-term accumulation of atmospheric CO2 and global greenhouse warming? Geology 21:1059-1062.
Velbel, M.A., 1992. Geochemical mass balances and weathering rates in forested watersheds of the southern Blue Ridge, III. Cation budgets and the weathering rate of amphibole. American Journal of Science, v. 292, p. 58-78.
RESEARCH & PUBLICATIONS: Publications include 31 articles and 50 abstracts. Research emphasizes determination of rates and mechanisms of mineral-water interactions in various compartments of the rock cycle, primarily of silicate minerals at surface and near-surface temperatures (e.g., weathering, groundwater environments), with secondary focii involving higher temperatures (e.g., burial diagenesis of sandstones) and highly soluble non-silicate minerals (e.g., halite & other evaporite minerals).
Quantification of rates of mineral-water reactions from thermodynamic and kinetic modeling of solute data, primarily from small forested watersheds. Ongoing and recently completed projects include:
Mechanisms, stoichiometries, and rates of weathering reactions involving ferromagnesian silicate minerals; compositional determinants of rate-limiting mechanisms and alteration textures during silicate mineral weathering and diagenesis; effect of temperature on mineral weathering rates in natural systems, and implications for global-change models; mineralogic, thermodynamic, kinetic, and hydrologic factors influencing discrepancies between lab and field rates of mineral-water interactions; mathematical forward and inverse models of mineral weathering rates in small hydrologic catchments; mineral weathering rates and clay-mineral formation in watersheds of the southern Blue Ridge & the Colorado Rockies; role of element uptake by forest biota on silicate-mineral weathering rates; formation of evaporite and oxide minerals by terrestrial weathering of Antarctic meteorites; burial diagenesis of rift-valley redbed sequences.
Curriculum Vitae: MICHAEL ANTHONY VELBEL
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