Many craters and thick regoliths of the moon imply that it has experienced heavy meteorite bombardments. Although the existence of a high-pressure polymorph is a stark evidence for a dynamic event, few high-pressure polymorphs are found in a lunar sample. α-PbO2 -type silica (seifertite) is an ultrahigh-pressure polymorph of silica, and is found only in a heavily shocked Martian meteorite. Here we show evidence for seifertite in a shocked lunar meteorite, Northwest Africa 4734. Cristobalite transforms to seifertite by high-pressure and -temperature condition induced by a dynamic event. Considering radio-isotopic ages determined previously, the dynamic event formed seifertite on the moon, accompanying the complete resetting of radio-isotopic ages, is ∼2.7 Ga ago. Our finding allows us to infer that such intense planetary collisions occurred on the moon until at least ∼2.7 Ga ago.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)