NASA's Phoenix Mars Lander is scheduled to land near the Red Planet's north pole just before 5 P.M. Pacific time (8 P.M. Eastern) on Sunday. The agency said that Phoenix is on course to touch down within eight miles (13 kilometers) of the center of its elliptical landing site, "Green Valley," located at 68 degrees north latitude and 233 degrees east longitude, where it will dig into a layer of rock-solid ice thought to lie near the surface. The vehicle is slated for a three-month tour to study the history of water on Mars.
Phoenix will enter Mars's atmosphere at a speed of roughly 12,750 miles (20,520 kilometers) per hour. During the next "seven minutes of terror," it will slow from a combination of contact with the atmosphere, drag from a parachute and bursts from its thrusters [see video below]. If it lands successfully, it would be the first craft to set down on Mars under its own power since the Viking 2 lander in September, 1976. NASA's last rocket engine–powered landing attempt—the Mars Polar Lander—crashed to its doom in December 1999.
The earliest time that mission controllers could hear back from Phoenix after landing is 4:53 P.M. Pacific time on Sunday.