NASA wants spacecraft for Mars return trip

coondoggie writes: If we ever do get to Mars, getting home might prove to be as difficult. NASA today selected three companies — Alliant Techsystems, Lockheed Martin and Northrop Grumman — to being the task of defining the spacecraft that will leave Mars, presumably at first loaded with red planet rock samples, then later possibly humans — for a safe trip back to Earth.

The engineering challenges those three companies face are immense