Carbonaceous chondrite meteorites experienced fluid flow within the past million years

1Lucy McGee,2,3Munir Humayun,1John Creech,4,5Brigitte Zanda
Science 371, 164-167 Link to Article [DOI: 10.1126/science.abc8116]
1Department of Earth and Environmental Sciences, Macquarie University, Sydney, NSW 2109, Australia.
2Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, FL 32310, USA.
3National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA.
4Institute de minéralogie, de physique des matériaux et de cosmochemie, Muséum National d’Histoire Naturelle, 75005 Paris, France.
5Institute of celestial mechanics and ephemeris calculations, Observatoire de Paris, 75014 Paris, France.
Reprinted with Permission from AAAS

Carbonaceous chondritic meteorites are primordial Solar System materials and a source of water delivery to Earth. Fluid flow on the parent bodies of these meteorites is known to have occurred very early in Solar System history (first <4 million years). We analyze short-lived uranium isotopes in carbonaceous chondrites, finding excesses of 234-uranium over 238-uranium and 238-uranium over 230-thorium. These indicate that the fluid-mobile uranium ion U6+ moved within the past few 100,000 years. In some meteorites, this time scale is less than the cosmic-ray exposure age, which measures when they were ejected from their parent body into space. Fluid flow occurred after melting of ice, potentially by impact heating, solar heating, or atmospheric ablation. We favor the impact heating hypothesis, which implies that the parent bodies still contain ice.

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