Pinpointing the Source of a Lunar Meteorite: Implications for the Evolution of the Moon

Abstract

The lunar meteorite Sayh al Uhaymir 169 consists of an impact melt breccia extremely enriched with potassium, rare earth elements, and phosphorus [thorium, 32.7 parts per million (ppm); uranium, 8.6 ppm; potassium oxide, 0.54 weight percent], and adherent regolith. The isotope systematics of the meteorite record four lunar impact events at 3909 ± 13 million years ago (Ma), ∼2800 Ma, ∼200 Ma, and <0.34 Ma, and collision with Earth sometime after 9.7 ± 1.3 thousand years ago. With these data, we can link the impact-melt breccia to Imbrium and pinpoint the source region of the meteorite to the Lalande impact crater.