University of New Mexico researchers have identified a 2.9 billion-year-old lunar meteorite, the youngest dated lunar rock.
University of New Mexico researchers have identified a 2.9 billion-year-old lunar meteorite, the youngest dated lunar rock. "It was a little piece of rock containing various minerals," said earth and planetary sciences department senior research scientist Lars Borg. "It's not much different than what's on earth." UNM's sample, obtained from the Natural History Museum in London, was named Northwest Africa 773, or NWA 773, to describe where it was found in 2000. NWA 773 is a 633-gram lunar meteorite made of impact breccia containing an olivine-rich clast. The bulk of the sample, 48 percent, was made of olivine, interpreted to be of igneous origin. The last stage of crystallization of an ocean of lunar molten rock produces materials strongly enriched in incompatible elements and phosphorus, termed KREEP. The materials are typical of the moon's western hemisphere. A large amount of the naturally occurring radioactive isotopes samarium and neodymium enabled UNM's team to date the meteorite. "We use geochronology to date lunar and Martian meteorites," Borg said. "The sample looked interesting as soon as we started working on it." The researchers washed and crushed part of the sample to help remove impurities and contaminants from the African desert.
"It allowed us to separate all other 'junk' found in the rock," Borg said. "We used ion chromatography to separate out elements of interest." The team's work confirmed NWA 773 was the youngest crystallization age from previously dated lunar samples by about 250 million years.
"At UNM we have a state-of-the-art laboratory to perform these types of studies. There is only one other lab in the world that can do the analyses at this level NASA (news - web sites)," Borg said. UNM's research recently was featured in Nature magazine. The research was funded through the NASA Cosmochemistry program.