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Fiery old geysers FOUND ON MOON: Volcanic past explained

Still don’t believe we went there?

The night sky on Earth in its early years was very different, with our Moon glowing red with fire in the sky. Now scientists think they've worked out why.

Back when the Moon was forming, the surface was alive with fiery geysers that spurted molten rock high in the low-gravity skies as the orbiting mass cooled and crusted over. These "fire fountains" can be seen today in places like Hawaii, and are driven by volatile substances going gaseous in the heat of the liquid rock.

Until mankind actually got some local rock samples, there was no way to tell what drove this volcanic process on the Moon. Now a team from Brown University and the Carnegie Institution for Science have analyzed rock samples from the Apollo 15 and 17 moon landings using a specially-developed scanning technique, and think they have the culprit – it's carbon.

The team built an ion probe that increased the ability to detect carbon twofold, and found 44 to 64 parts per million in the samples. That level of carbon on the moon would have caused the geysers, according to software models that were augmented with high-pressure molten rock testing in the lab.

Magma in Moon rock

Preserved magma in Moon rock samples turns up carbon

"Most of the carbon would have degassed deep under the surface," said Alberto Saal, associate professor of earth, environmental, and planetary sciences at Brown.

"Other volatiles like hydrogen degassed later, when the magma was much closer to the surface and after the lava began breaking up into small globules. That suggests carbon was driving the process in its early stages."

In a paper published in Nature Geoscience, the team suggests that carbon bubbled up from the lunar surface by fusing with oxygen to become carbon monoxide, which powered the geysers. The gas has long since escaped from the Moon's tenuous atmosphere.

The type of rock most similar to the Moon samples is found in the mid-ocean ridges that form down the spines of our seas by molten rock oozing from cracks in the crust deep underwater. Rock samples from there match the Moon rock in carbon, hydrogen, and other volatiles, and the team posits this may be more evidence that the Earth and Moon share a common composition.

There's a growing body of evidence to suggest that our moon was formed when a large body, possibly the size of Mars, collided with the proto-Earth. The impact left a moon-sized amount of debris that coalesced just like Earth, although there are alternative scenarios.

"The volatile evidence suggests that either some of Earth's volatiles survived that impact and were included in the accretion of the Moon, or that volatiles were delivered to both the Earth and Moon at the same time from a common source – perhaps a bombardment of primitive meteorites," Saal said.

The research highlights just how much we've learned about the Moon – and our own planet – since going there, and how much we've missed. Apollo 17, which delivered some of these samples, was the only mission to carry a trained scientist. On that last mission, geologist Harrison Schmitt's forays across the lunar surface gathered a wealth of evidence that is still turning out surprises today. ®

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