Lee, M. R. , Hallis, L. J. , Daly, L. and Boyce, A. J. (2023) The water content of CM carbonaceous chondrite falls and finds, and their susceptibility to terrestrial contamination. Meteoritics and Planetary Science, 58(12), pp. 1760-1772. (doi: 10.1111/maps.14099)
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Abstract
CM carbonaceous chondrites can be used to constrain the abundance and H isotopic composition of water and OH in C-complex asteroids. Previous measurements of the water/OH content of the CMs are at the higher end of the compositional range of asteroids as determined by remote sensing. One possible explanation is that the indigenous water/OH content of meteorites has been overestimated due to contamination during their time on Earth. Here we have sought to better understand the magnitude and rate of terrestrial contamination through quantifying the concentration and H isotopic composition of telluric and indigenous water in CM falls by stepwise pyrolysis. These measurements have been integrated with published pyrolysis data from CM falls and finds. Once exposed to Earth's atmosphere CM falls are contaminated rapidly, with some acquiring weight percent concentrations of water within days. The amount of water added does not progressively increase with time because CM falls have a similar range of adsorbed water contents to finds. Instead, the petrologic types of CMs strongly influence the amount of terrestrial water that they can acquire. This relationship is probably controlled by mineralogical and/or petrophysical properties of the meteorites that affect their hygroscopicity. Irrespective of the quantity of water that a sample adsorbs or its terrestrial age, there is minimal exchange of H in indigenous phyllosilicates with the terrestrial environment. The falls and finds discussed here contain 1.9–10.5 wt% indigenous water (average 7.0 wt%) that is consistent with recent measurements of C-complex asteroids including Bennu.
| Item Type: | Articles |
|---|---|
| Additional Information: | This work was funded by the UK Science and Technology Facilities Council through grants ST/T002328/1, ST/T506096/1 and ST/W001128/1, and the UK Natural Environment Research Council through NEIF Facility award 2406.0231. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Daly, Dr Luke and Boyce, Professor Adrian and Hallis, Dr Lydia and Lee, Professor Martin |
| Authors: | Lee, M. R., Hallis, L. J., Daly, L., and Boyce, A. J. |
| College/School: | College of Science and Engineering > School of Geographical and Earth Sciences College of Science and Engineering > Scottish Universities Environmental Research Centre |
| Journal Name: | Meteoritics and Planetary Science |
| Publisher: | Wiley |
| ISSN: | 1086-9379 |
| ISSN (Online): | 1945-5100 |
| Published Online: | 12 November 2023 |
| Copyright Holders: | Copyright: © 2023 The Authors |
| First Published: | First published in Meteoritics and Planetary Science 58(12):1760-1772 |
| Publisher Policy: | Reproduced under a Creative Commons licence |
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