The last two rovers the U.S. sent to Mars are still running more than four years later. The next one, the Mars Science Laboratory (most boring rover name ever!), is even tougher. Launching in 2009, it is 9 ft. (2.7 m) long, runs on a chunk of plutonium and carries 176 lb. (80 kg) of scientific instruments, including a neutron gun — for firing at the ground to detect permafrost, not at hostile Martians.