Hydrogen isotope ratios in lunar rocks indicate delivery of cometary water to the Moon
Abstract
Water plays a critical role in the evolution of planetary bodies, and determination of the amount and sources of lunar water has profound implications for our understanding of the history of the Earth-Moon system. During the Apollo programme, the lunar samples were found to be devoid of indigenous water. The severe depletion of volatiles, including water, in lunar rock samples has long been seen as strong support for the theory that the Moon formed during a giant impact event. Water has now been identified in lunar volcanic glasses and apatite, but the sources of water to the Moon have not been determined. Here we report ion microprobe measurements of water and hydrogen isotopes in the hydrous mineral apatite, derived from crystalline lunar mare basalts and highlands rocks collected during the Apollo missions. We find significant water in apatite from both mare and highlands rocks, indicating a role for water during all phases of the Moon's magmatic history. Variations of hydrogen isotope ratios in apatite suggest sources for water in lunar rocks could come from the lunar mantle, solar wind protons and comets. We conclude that a significant delivery of cometary water to the Earth-Moon system occurred shortly after the Moon-forming impact.
- Publication:
-
Nature Geoscience
- Pub Date:
- February 2011
- DOI:
- 10.1038/ngeo1050
- Bibcode:
- 2011NatGe...4...79G