The formation of ancient rocks on the Moon may be directly linked to large-scale meteorite impacts, concludes a group of international scientists led by the Royal Ontario Museum after research a unique rock collected by NASA astronauts during the 1972 Apollo 17 mission to the Moon. The rock contains mineralogical evidence that it formed at incredibly high temperatures, in excess of 2300 °C/ 4300 °F, that could have been achieved by the melting of the outer layer of a planet in a large-impact event, reports Science Daily.
Researchers discovered in the rock the presence of a mineral known as baddeleyite, a stable phase arising from cubic zirconia, commonly used on earth as a substitute for diamonds in jewelry, which could have been formed only in rocks heated to above 2300 °C. While examining the structure of the crystal, the researchers measured the age of the grain, which reveals the baddeleyite formed over 4.3 billion years ago. Given that the high-temperature cubic zirconia phase must have formed before this then, they concluded that large impacts were critically important to forming new rocks on the early Moon.
“Rocks on Earth are constantly being recycled, but the Moon doesn’t exhibit plate tectonics or volcanism, allowing older rocks to be preserved,” explains Dr. Lee White, Hatch Postdoctoral Fellow at the Museum. “By studying the Moon, we can better understand the earliest history of our planet. If large, super-heated impacts were creating rocks on the Moon, the same process was probably happening here on Earth.”
Adds Dr. James Darling, a reader at the University of Portsmouth and co-author of the study. “These unimaginably violent meteorite impacts helped to build the lunar crust, not only destroy it.”