Unusual minerals in the centre of many impact craters on the Moon could come from the impacting object themselves, reports a study published online this week in Nature Geoscience. These minerals were previously thought to have been exhumed from beneath the lunar surface by the impact.
Jay Melosh and colleagues used a computer model to simulate the collision of meteoroids with the lunar surface. Ordinarily, meteoroids are thought to be vaporized on impact. However, the simulations show that fragments of the meteoroid can survive at low impact velocities. Following the explosive impact, the meteoroid fragments can be swept back into the crater. The results imply that the unusual minerals once thought to be representative of the lunar interior may not be indigenous to the Moon.
In an accompanying News and Views article, Erik Asphaug writes that the study “raises the possibility of finding early Earth material, ejected by collisions billions of years ago, in massive deposits on the Moon.”