The presence of strange minerals in the center of the moon's craters may be bits and pieces of shattered space rocks that actually made those craters, as opposed to exhumed bits of the moon's interiors, as previously speculated.
Unusual minerals like spinel and olivine have been found on the surface of many lunar craters, and studies suggest that these minerals are actually nothing but common components of meteorites and asteroids. Since they rarely hit the moon's surface, it was believed that these meteorites vaporize in getting in contact with large celestial bodies.
This new finding, published in the journal Nature Geoscience, may prove to be a revelation, but may also cast a cloud of doubt about what we already knew about the moon.
The researchers stimulated some slow impacts with high angles, and were surprised to see what they could. They discovered that when a slow impact happened at the speed of less than 27,000 miles an hour, the rocks don't vaporize. Instead, they shatter into a rain of debris that is swept back down the crater sides and piles up into the crater's central peak.
"Nobody has done it at such high resolution," planetary scientist Jay Melosh of Purdue University, said.
"This raises the possibility of finding early Earth material, ejected by collisions billions of years ago, in massive deposits on the moon, and suggests yet another explanation for the spinels: that they are deposits derived from the Earth's upper mantle, emplaced long ago on to the moon and reworked," Erik Asphaug of Arizona State University writes in an accompanying commentary in the same issue of Nature Geoscience.
The team has therefore, finally concluded that the presence of unusual minerals on the surface of the moon's craters are not its own, but exports of asteroids and meteoroids.
This new impact modeling may help explore the possibility of pockets of the early Earth being on the moon.
"Even more provocative," Asphaug explained, "is the suggestion that we might someday find Earth's protobiological materials, no longer available on our geologically active and repeatedly recycled planet, in dry storage up in the lunar 'attic'."