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John Kierein
2004-Nov-19, 01:03 PM
http://antwrp.gsfc.nasa.gov/apod/ap041119.html

What causes the parallel lines on Phobos? Is it layered? Or does debris from collisions roll along the surface normal to the spin axis? Any ideas?

Wolverine
2004-Nov-19, 10:15 PM
Here's (http://www.lpi.usra.edu/publications/slidesets/3dsolarsystem/slide_30.html) one idea on the matter.

Edited to add: more here (http://www.planetary.org/news/2004/phobos_mex_1112.html) and here (http://www.esa.int/SPECIALS/Mars_Express/SEM21TVJD1E_0.html).

Nethius
2004-Nov-20, 12:29 AM
Yes, I've wondered this myself! If it was fractures from a collision, wouldn't all the lines somewhat head in the direction of the crater? (I'm no expert so please explain if I'm wrong) I guess most of the lines are concentrated at the "bottom"

If I may, I'd like to add another question. Would an impact that big not cause it to leave what ever orbit it was in? Or, maybe Phobos was a stray astroid, and the collision threw it into Mars orbit?

What ever the case, Phobos is very intereting! Thanks for posting this topic!

slinted
2004-Nov-20, 04:20 AM
I hope we see more imagery of Phobos as we get more orbiters around Mars. Its a facinating target with a lot of potential scientific interest. One of the most interesting facts to me is its extreme closeness to Mars itself, orbiting at 5,800 km from the surface.
Given the recent ESA findings regarding Mars' atmosphere streaming off the surface due to solar wind ( http://www.esa.int/SPECIALS/Mars_Express/SEM75BADFZD_0.html ), I now wonder what kind of interaction Phobos has with that atmospheric breeze coming off the planet as it travels around Mars every 7 (earth) hours.

fossilnut
2004-Nov-25, 10:14 PM
The lines are not any lot different than those one would find on a rock you can hold in your hand if it had undergone the same energy impact. I'm guessing the moon is just a big chunk of carbonates and ice. If it's made of this and there's that big crater (forget the name) then it would be more amazing if there were NO shock lines. If made harder materials then Phobos would have shattered into fragments.