Phoenix Mars Prepares for Landing

NASA's Phoenix Mars Lander will land near the north pole as it completes its 10-month voyage.

NASA's Phoenix Mars Lander has sailed through 419 million miles of space since launching last summer and has 3 million miles to go before Sunday's touchdown. If successful, it would be the first spacecraft to set down on the Red Planet's high northern latitudes.

"We've had a very clean flight to Mars through this point," said Ed Sedivy, program manager at Lockheed Martin Corp., which built Phoenix.

Landing on Mars is challenging: More than half of all attempts have ended in disaster.

NASA hopes to have a trio of operating robots on Mars. Unlike the twin rovers Spirit and Opportunity, which landed in equatorial regions in 2004, Phoenix will be stationary.

For Phoenix to be successful, it will have to survive a 12,000-mph plunge into the atmosphere and use friction and a parachute to slow down.

The Mars robotic dirt and ice digger will attempt a soft landing with the help of pulsing retro rockets designed to guide it gently to the surface. By contrast, the rovers used parachutes and cushioned air bags that bounced and rolled across the surface.

NASA has not had a successful powered landing in more than three decades since the twin Viking spacecraft fired their thrusters in 1976. The last time the space agency attempted a powered landing was during the 1999 Mars Polar Lander mission, which ended in failure when the spacecraft prematurely shut off its engines.

Phoenix is set to touch down in a broad, shallow valley in the northern arctic region believed to hold a vast storage of underground ice.

The three-legged probe will dig trenches in the icy soil and study whether liquid water ever existed at the site. It will also search for traces of organic compounds.

"There is no signpost today that says 'Land here. This is the best spot,'" Smith said.

Phoenix, named after the mythological bird that rises from its ashes, is pieced together from a lander mission that NASA scrapped after the Polar Lander failure.