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The Flux of Meteorites to the Earth: Determinations by Terrestrial Techniques |
1 Department of Earth and Planetary Sciences, Western Australian Museum, Francis Street, Perth, WA 6000, Australia
2 Department of Physics and Astronomy, Kelvin Building, University of Glasgow, University Avenue, Glasgow G12 8QQ, UK
3 Department of Physics, The Open University, Milton Keynes, MK7 6AA, UK
4 Department of Chemistry, The Open University, Milton Keynes, MK7 6AA, UK
5 Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, UK
6 Planetary Science Research Institute, The Open University, Milton Keynes, MK7 6AA, UK
Meteorite accumulation sites offer the prospect of observing changes in flux over time; however, two main problems must be overcome: calculating a decay constant for samples in an area, and providing accurate pairing data, such that the number of true meteorites (not fragments) can be ascertained. We have used a comparison of meteorite terrestrial age and weathering data to constrain decay constants for hot desert meteorite populations. Meteorites resident in these sites typically have terrestrial ages <50 ka. Our estimates of the flux of meteorites to the Earth are within a factor of 2–3 of independent estimates made by the Meteorite Observation and Recovery Project network, and suggest no change in the flux over the last 50 ka. A similar approach applied to meteorites from Allan Hills, Antarctica, finds much lower levels of weathering, although terrestrial ages for these samples are much longer. We also observe a correlation between terrestrial age and degree of weathering in the Allan Hills meteorites, suggesting a weathering rate 2–3 orders of magnitude slower than values typical of hot desert sites. Given that blue ice regions are subject to some horizontal flow, we propose a model in which the observed oxidation-terrestrial age distribution is largely a result of ice movement, rather than weathering. Comparing oxidation and terrestrial age data in the Antarctic and hot desert accumulations, we estimate a lifetime for the Allan Hills population of 200–300 ka. Given the distance to the nearest ice divide (200 km), this suggests an average horizontal flow rate of 1 m a–1. This approach may allow an estimate of the catchment area for these samples to be made. In addition, we suggest an alternative method for pairing samples which makes use of automated image processing and data analysis of reflected light photomicrographs to acquire a ‘textural fingerprint’ of a sample, and a genetic algorithm to compare the numerous data variables.
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