A younger Moon

摘要

It was almost 40 years ago that we found out what the Moon is made of: lunar samples collected during the Apollo missions turned out to consist of rocky material similar in composition to that found on Earth. We also think we know that the Moon formed from the accretion of molten and vaporized ejecta produced by a collision between proto-Earth and a giant Mars-sized impactor. But the answer to the 'When?' of Moon formation has remained elusive. On page 1206 of this issue, Touboul et aV examine this question with tungsten-isotope measurements of lunar rocks.