Tuesday, September 28, 2010

Phobos: Moon of Mars Formed From Rubble?

"Mars Moon Phobos Likely Forged by Catastrophic Blast"
Space.com (September 27, 2010)

"One of the two moons of Mars most likely formed from rubble catapulted into space after a comet or meteorite slammed into the Red Planet, a new study finds.

"The moon, Phobos, looks a lot like an asteroid: It's lumpy, potato-shaped and very small. It has an average radius of just 11 kilometers (6.8 miles).

"Scientists have long wondered about the origin of Phobos — is it merely a captured asteroid, the leftovers from Mars' formation or evidence of a cosmic Martian hit-and-run with another object?

"The new study found that the moon's composition and density strongly indicate that, like the leading theory for Earth's own moon, Phobos is the result of a catastrophic impact with its parent planet...."

If Phobos is essentially a loose rubble pile, with open spaces left over from its formation, that would help explain why the Stickney Crater impact didn't shatter it. Hit a solid rock with a hammer - you may end with several smaller rocks. Hit a pile of gravel with a hammer - you'll get a pile of gravel with a dent in it.

Another indication that Phobos isn't from the Asteroid Belt is that it's chemically similar to the surface of Mars - including minerals that form when there's liquid water around.

We may know more, if the Russian Phobos-Grunt ("grunt" is "soil" in Russian) mission successfully scoops up some of the surface of that moon of Mars.

Related posts:More posts about Mars:

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