MICHELE NORRIS, Host:
Now, decades later, scientists have found a surprise inside that dirt which may teach us something new about the birth of the moon. NPR's Nell Greenfieldboyce reports.
NELL GREENFIELDBOYCE: Back in 1972, Harrison Schmitt was walking on the moon when he suddenly saw something shocking. It was a color.
HARRISON SCHMITT: It's all over. (Unintelligible)
GREENFIELDBOYCE: Schmitt and his fellow moonwalker, Eugene Cernan, could hardly believe it.
EUGENE CERNAN: It is. I can see it from here. It's orange. It's crazy.
GREENFIELDBOYCE: The astronauts scooped some up. Back on earth, scientists realized that the orange color came from bits of glass.
ERIK HAURI: Erik Hauri is a geochemist. He says volcanoes made the glass a few billion years ago, when the moon was young.
HAURI: And these glasses are circular or spherical beads that form when the lava is ejected at high velocity out of the erupting crater and cools so quickly that it quenches to a glass in the air before it falls back to the surface.
GREENFIELDBOYCE: The glass beads come in different colors. They've been analyzed before, but Hauri and his colleagues wanted to take a fresh look to see if the beads contained any water. Some moon experts thought there was no way they'd find any.
HAURI: We got a lot a lot of comments like, oh, well, we already know that the moon is dry, you know, we've known this for 20 years,.
GREENFIELDBOYCE: People thought the moon was dry because of how it formed.
HAURI: Through a process called giant impact.
GREENFIELDBOYCE: Scientists believe the moon was born 4.5 billion years ago, when an object the size of Mars came hurtling out of the void and smacked the young Earth. This melted both objects and put a cloud of debris around the Earth. That became the moon. The new moon was hot, like a sea of magma.
HAURI: The prevailing idea has been that there's no way a completely molten moon could have retained any water.
GREENFIELDBOYCE: But Hauri thought, well, let's just see. He has an instrument in his lab at the Carnegie Institution of Washington that's very sensitive. He blasted molecules off the glass beads and found that some of those molecules were water molecules. According to a report in the journal Nature, it wasn't a lot of water, less than 50 parts per million, but from this, the researchers can estimate that way back when, the interior of the moon probably contained as much water as the Caribbean Sea. Hauri says this is a problem for the giant impact theory.
HAURI: It's really hard to imagine a scenario in which a giant impact melts completely the moon, and at the same time allows it to hold onto its water, and that's a really, really difficult knot to untie.
BEN BUSSEY: It's obviously a very new result to say that the moon might have had a significant amount of water right after it formed.
GREENFIELDBOYCE: Ben Bussey is a planetary scientist at the Johns Hopkins University Applied Physics Lab. He says besides raising questions about the giant impact theory, the finding raises another question too. Scientists have seen hints of ice at the moon's poles, in cold, shadowed craters. Everyone has thought this ice had to come from outside the moon, probably from meteorite impacts, but maybe some of it came from inside the moon.
BUSSEY: There is a chance that there might be some very old water of the type that they discuss in the paper.
GREENFIELDBOYCE: If the moon does have ice, he says scientists could figure out where it came from, but only if a rover or an astronaut went to get a sample. Nell Greenfieldboyce, NPR News.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.