PARIS – Minerals found in craters on the moon may be remnants of asteroids that slammed into it and not, as long believed, the satellite’s innards exposed by such impacts, a study said Sunday.
The findings, published in the journal Nature Geoscience, cast doubt on the little we know about what the moon is actually composed of.
It had long been thought that meteoroids vaporize on impact with large celestial bodies.
Unusual minerals like spinel and olivine found in many lunar craters, but rarely on the moon’s surface, were therefore attributed to the excavation of subsurface lunar layers by asteroid hits.
Olivine and spinel are common components of asteroids and meteorites, and have been found on the floors and around the central peaks of lunar craters like Copernicus, Theophilus and Tycho that are around 100 km in diameter. On Earth, spinel and olivine create rare gemstones like peridot.
A team from China and the United States simulated the formation of moon craters and found that at impact velocities under 12 km per second, a projectile may survive the impact, though fragmented and deformed.
Co-author Jay Melosh from Purdue University in Indiana, said the finding answers the conundrum exposed by earlier studies, which said craters the size of Copernicus were not big enough to have dredged up the contents of the moon’s deep, interior mantle.
In an article commenting on the study, Erik Asphaug, of the School of Earth and Space Exploration at Arizona State University, said the theory meant that material excavated from Earth by large impacts during the planet’s early days may still be found on the moon.
“Even more provocative is the suggestion that we might someday find Earth’s proto-biological materials, no longer available on our geologically active and repeatedly recycled planet, in dry storage up in the lunar ‘attic,’ ” Asphaug said.
“Certainly, the potential of finding early Earth material is emerging as one of the primary motivations for a return to the moon by human astronauts in our ongoing search for the origin of life.”