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—842 pounds 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 analyzed 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 center, 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]
Image by NASA
