NASA's Mars Phoenix Lander is set to explore the Martian arctic, looking for signs of water and conditions favorable to life. But getting there won't be easy: in the international history of the space age, only five of 13 attempts to land on Mars have succeeded.

Phoenix will enter the Martian atmosphere at nearly 13,000 miles per hour, kicking off a seven-minute series of events that must slow the lander to five miles an hour before it's three legs reach the ground. It's the first attempt at a powered landing on Mars since the Viking missions of 1976.