We're used to thinking of the moon as a cold and unassuming lump of rock — but new research suggests that it could have been made of a strange magma mush for hundreds of millions of years before it solidified into the object we now see every night.
Professor Sara Russell, head of the mineral and planetary sciences division at the Natural History Museum in London, thinks that previous suggestions of how the moon formed are biassed, reports Space. Based on a samples of rock — 380kg in total — brought back from the moon by the Apollo missions, the current theory suggests that the moon was completely molten right after its formation, 4.5 billion years ago. This 'magma ocean', so the theory goes, then cooled and solidified.
But those samples came from a relatively small area of the moon's near side, and Russell has long suspected that an alternative formation theory may be more appropriate. She explains to Space:
"The traditional view of the evolution of the moon is quite simplistic — that it was molten and then it solidified. But we're saying it's not really true, and that the moon was always a very complicated geological object."
Russell and her team have analysed numerous lunar meteorites, and her observations suggest that the moon didn't crystallize from the same pool of molten rock. She explains:
"Rocks we see on the surface of the moon now are not products of a magma ocean, so we don't know if there was one [a magma ocean], as we don't have any rocks from that time. But there has been a lot of volcanism on the moon, a lot of messing about of the rocks — and maybe extensive volcanism that was overlaying more volcanism could have been responsible for forming some of these anorthosites."
So, instead of being completely molten, Russell believes that the satellite was in fact made up of a 'magma mush': a mixture of semisolid and liquid, with a solid crust. The centre, she believes, remained hot, causing constant volcanic activity, spewing lava over the moon's surface, and in turn slowly building new layers of rock, one on top of the other.
Not everyone believes she's right though. "Certainly it looks like the formation of the lunar crust was more complex than once thought," explained Ian Crawford, a professor of planetary science and astrobiology at Birkbeck College, University of London to Space. "But it is too soon to ditch the magma ocean hypothesis, as it explains a lot."
The way to settle it? More, less biased samples from the moon. Get a move on, NASA. [Space]