Decent general article on molybdenum; I picked this one over Web Elements entry, as there's not too much info on the uses of the metal therein:
http://en.wikipedia.org/wiki/MolybdenumI'd assume the Deimos has a molbdenum alloy as it's armor plating for practical purposes... As a pure element, "moly" has the sixth highest melting point of any pure element. It also has laudable thermal expansion properties. Tungsten is second in line in terms of melting point, but seeing as it's much more brittle, molybdenum is probably a better choice.
The more you know...