Your impression of the moon might just be a mirage.
Geology Prof. Youxue Zhang is part of a research team that recently discovered plagioclase mineral moon rocks that contain up to six parts per million of water — a finding that could have much larger implications.
“By the nature of the mineral, it should not even have the very low water concentration,” Zhang said.
Zhang and his team have been studying plagioclase from the moon’s crust obtained during the Apollo missions between 1961 and 1972. These rocks would have been part of the Genesis region of the moon.
The finding is important because, according to the current theory of moon formation — giant impact theory — the moon formed when hot meteors collided with Earth, forming an ocean of molten lava that cooled to form the moon. Zhang said all water should have been lost in this process.
“Now, when we’ve found so much water in the great early moon, it’s difficult to reconcile with the giant impact hypothesis,” he said.
The first detection of water on the moon occurred in 2008, but that water was contained in more recent moon rocks, and could have been contaminated by other factors like meteorites and comets.
“Just in the last couple years we have been working on this,” Zhang said. “It’s one surprise after another. It’s just very exciting.”
Hejiu Hui, postdoctoral research associate at the University of Notre Dame, was the member of the research team who pushed for the project. Hui received his Ph.D. under Zhang at Michigan.
Hui said it has taken a long time to make this discovery because there was no obvious evidence of any water during the Apollo missions.
“Through the Apollo missions, people didn’t see any liquid water on the moon,” Hui said.
While better technology also allowed for the water to be found, even he was skeptical of the finding at first and thought it could be contamination. Zhang said Hui persisted in the research and the finding has proved important.
Zhang and Hui both said this finding might lead to a revision of the giant impact theory, adding that there are no current theories that provide a better explanation.
“Impact formation scenario is still the best theory for the moon formation, but the problem is we need to reconcile the hydrogen — the water — with other volatile elements,” Hui said.
Hui asked Clive Neal, a professor of geology at Notre Dame, to join the team in order to help interpret the data findings.
It’s still too soon to say if the results are correct.
“It’s early days yet to say everything we knew about the moon was wrong,” Neal said. “It may be that we need to adjust those models of giant impact and magna ocean a little bit rather than say, ‘oh, no, they cannot have occurred.’”
Neal said he is excited to see what will come of this new research.
“The moon itself is still revealing new secrets to us even though Apollo ended in 1972 … we’re still understanding a lot more about our nearest neighbor.”
—Follow Danielle Raykhinshteyn on Twitter at @dannierayh.