- A unique meteorite that fell on a Soviet military base
in Yemen in 1980 may have come from one of the moons of Mars. Several
meteorites
from the Red Planet have been found on Earth, but this could be the only
piece of Martian moon rock.
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- Andrei Ivanov, who is based at the Vernadsky Institute
of Geochemistry and Analytical Chemistry in Moscow, Russia, spent two
decades
puzzling over the fist-sized Kaidun meteorite before he decided that it
must be a chip off Phobos, the larger of the two Martian moons. "I
can't find a better candidate," Ivanov told New Scientist.
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- The Kaidun meteorite is like no other in the world and
23,000 of them have been catalogued. It is made of many small chunks of
material, including minerals never seen before.
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- Working with Michael Zolensky of the NASA Johnson Space
Center in Houston, Texas, Ivanov used an electron microscope to look at
the space rock's crystal structure, peered through its minerals using
X-rays
and vaporised fragments to catalogue the elements inside. And every sample
turned out to be something "new and weird", says Zolensky.
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- Volcanic debris
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- Among the odd materials in the meteorite were two
fragments
of volcanic rock which only forms in massive, planet-like bodies with a
core, mantle and crust. But much of the meteorite is a kind of carbon-rich
material that only occurs in asteroids.
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- Zolensky thinks this paradox could be resolved if the
meteorite comes from a Martian moon. Both Phobos and Deimos are thought
to be asteroids captured by Mars as they wandered through space. That would
explain the carbonaceous material.
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- And the pieces of volcanic rock could be bits of Mars,
thrown into orbit when other asteroids crashed into the planet. Phobos
is the more likely candidate: it orbits only 6000 kilometres from the
planet's
surface, much closer than Deimos, and so has probably mopped up a lot more
fragments of Mars rock.
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- The idea is plausible, if somewhat speculative, says
Sara Russell, a meteorite expert at the Natural History Museum in London.
"There have been no landers sent to Phobos and so almost nothing is
known about the composition and geology of this body."
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- Zolensky thinks that an unusual asteroid could have been
the source. Hope of resolving the mystery rests with the European Space
Agency, which has been asked by UK scientists to consider sending a mission
to Phobos as part of its Mars exploration programme.
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- Journal reference: Solar System Research (vol 38, p
97)
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http://www.newscientist.com/news/news.jsp?id=ns99994902
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