May 11 (UPI) -- Parts of the moon's crust were forged by large and violent meteorite impacts, according to new research published Monday in the journal Nature Astronomy.
Analysis of a lunar rock, brought home by astronauts on NASA's 1972 Apollo 17 mission, revealed the presence of minerals that can only form at temperatures greater than 4,300 degrees Fahrenheit -- the kind of temperatures generated by large impact events.
Researchers found evidence of a specific phase of cubic zirconia inside the lunar rock, a phase only produced at high temperatures. The mineral has since reverted to baddeleyite, but the signature of its cubic zirconia phase remains imprinted in the structure of the baddeleyite crystals.
Scientists were able to date the baddeleyite to 4.3 billion years ago, which suggests the moon experienced a series of large impacts during this period.
Planetary scientists have long wondered how the moon came to feature such a unique diversity of rock types on its surface. Researchers still aren't certain what drove the mixing of the moon's outer and inner layers in the wake of its formation, but the latest research suggests a period of heavy bombardment by large meteors likely played a role.
"Rocks on Earth are constantly being recycled, but the moon doesn't exhibit plate tectonics or volcanism, allowing older rocks to be preserved," Lee White, lead author of the new study and a postdoctoral fellow at the Royal Ontario Museum, said in a news release.
"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," White said.
The baddeleyite grain analyzed by scientists measured less than a millimeter in length, but the tiny artifact is having a sizable impact on lunar science.
"This small grain is still holding the evidence for formation of an impact basin that was hundreds of kilometers in diameter," ROM research fellow Ana Cernok. "This is significant, because we do not see any evidence of these old impacts on Earth."