Phobos
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On September 29, a crazily-rotating, dumbbell-shaped
asteroid the size of a small city will pass closer to Earth than
any other asteroid this century?but it won't hit us. When
astronomers say asteroid Toutatis will come "close," they
mean it will be a million miles away from us.
The asteroids astronomers worry about are the ones that
pass between us and the moon?now THAT'S close! But a
million miles away is around 4 times the distance between
Earth and the moon. In space.com,
Robert Roy Britt writes: "Asteroid Toutatis, officially
numbered 4179, was discovered by French astronomers in
1989. Researchers can't predict far enough into the future to
rule out Toutatis ever slamming into Earth, so it is listed
officially as a Potentially Hazardous Asteroid. NASA says it
won't hit for at least the next six centuries."
We're worried about meteor impacts, but most of us never
stop to think about where these meteors come from. It's now
been discovered that a meteor that fell on a Soviet military
base in Yemen in 1980 came from one of the moons of Mars.
This is the only sample of Martian Moon rock that we have.
Jenny Hogan writes in New Scientist that geologist Andrei
Ivanov spent two years trying to figure out where the meteor
came from. Finally he decided it must be a chip off Phobos,
the largest of the two Martian moons. He says, "I can't find a
better candidate."
Of the 23,000 meteorites have been catalogued so far, none
of them is like the Kaidun meteorite, which contains minerals
that have never been seen before. Ivanov calls it "new and
weird."
It contains fragments of volcanic rock, which only forms in
large, planet-like bodies with a core, mantle and crust. This
could come from Martian volcanoes throwing rocks out into
the atmosphere. The rest of the meteorite is the same kind of
carbon-rich material that only occurs in asteroids. Both
Phobos and Mars' other moon Deimos are probably asteroids
that were captured by Mars as they passed by the planet,
which would explain why the meteorite has so much carbon.
The only explanation for all this is if it came from a Martian
moon.
Meteorite expert Sara Russell says, "There have been no
landers sent to Phobos and so almost nothing is known about
the composition and geology of this body." But the European
Space Agency is planning to go there soon.
There are many
strange mysteries right here on Earth, like why a certain CD
can free your imagination in totally new ways and greatly
enrich your dream life.
