Potassium isotopic evidence for a high-energy giant impact origin of the Moon

1,2Kun Wang, 3Stein B. Jacobsen
Nature 538, 487–490 Link to Article [doi:10.1038/nature19341]
1Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA
2Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri 63130, USA
3Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, Massachusetts 02138, USA

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An unusual occurrence of coesite at the Lonar crater, India

1Steven J. Jaret,1Brian L. Phillips,2David T. King Jr,1Tim D. Glotch,3Zia Rahman,4Shawn P. Wright
Meteoritics & Planetary Science (in Press) Link to Article [DOI: 10.1111/maps.12745]
1Department of Geosciences, Stony Brook University, Stony Brook, New York, USA
2Department of Geosciences, Auburn University, Auburn, Alabama, USA
3Jacobs—NASA Johnson Space Center, Houston, Texas, USA
4Planetary Science Institute, Tucson, Arizona, USA
Published by arrangement with John Wiley & Sons

Coesite has been identified within ejected blocks of shocked basalt at Lonar crater, India. This is the first report of coesite from the Lonar crater. Coesite occurs within SiO2 glass as distinct ~30 μm spherical aggregates of “granular coesite” identifiable both with optical petrography and with micro-Raman spectroscopy. The coesite+glass occurs only within former silica amygdules, which is also the first report of high-pressure polymorphs forming from a shocked secondary mineral. Detailed petrography and NMR spectroscopy suggest that the coesite crystallized directly from a localized SiO2 melt, as the result of complex interactions between the shock wave and these vesicle fillings.