Mars Polar Lander and Deep Space 2
Phoenix Mars Lander
A couple were destroyed due to malfunctions but crashed to the surface of Mars. The list does not currently include smaller objects such as springs, fragments, parachutes, heat shields and so on.
All this stuff would have already contaminated Mars by now! So why the fuss over contamination by Curiosity alone?
edit on 11-9-2012 by OrionHunterX because: (no reason given)