Phobos sample return?

Contributed by
Feb 11, 2007

This is too cool: the UK is thinking about a space probe that will go to Mars, land on the tiny moon Phobos, and return a sample to Earth.

I love this idea. Phobos is weird. It has and extremely low density (prompting some scientists years ago to colorfully speculate that it was a hollow alien spaceship!), it orbits Mars in a very low

retrograde orbit (atmospheric tidal drag is slowly dropping it, and it will impact Mars in a few million years), and it is heavily cratered with a whopper at one end. It's almost certainly a captured asteroid, and is worthy of further study.

Update: Phobos is not in a retrograde orbit; but it is so low that it orbits the planet faster than Mars rotates, so from the surface it appears to go backwards in the sky -- that's what I was thinking when I wrote that. Thanks for the commenters who pointed this out.

Update 2: Sigh. Reader Alan Harris pointed out it's tidal drag, not atmospheric drag, working on Phobos and dropping the orbit. D'oh!

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