Nasa's Mars spacecraft heads for north pole

Pasadena, California: A three-legged Nasa spacecraft was closing in on Mars on Sunday for what scientists hope will be the first-ever touchdown near Mars' north pole to study whether the permafrost could have supported primitive life.

The time it takes the Phoenix Mars Lander to streak through the atmosphere and set down on the dusty surface has been dubbed "the seven minutes of terror" for good reason. More than half of all attempts ever to land on Mars have ended in failures.

A little nervous

"I'm a little nervous on the inside. I'm getting butterflies," Peter Smith, principal investigator from the University of Arizona, Tucson, said on the eve of the landing.

"We bet the whole farm on this safe landing and we can't do our science without this safe landing."

Phoenix is preprogrammed to plummet through the Red Planet's hostile atmosphere, and will rely on the intricately choreographed use of its heat shield, parachute and rockets to slow its descent from over 19,300 km/h to a cautious 8km/h touchdown.

Nasa has not had a successful soft landing in more than three decades since the twin Viking landers in 1976. The last time the space agency tried was in 1999 when the Mars Polar Lander angling for the south pole crashed after prematurely cutting off its engines.

Phoenix was built from a lander that was scrapped after the Polar Lander disaster. Engineers spent years testing Phoenix to resolve all known problems, but there are no guarantees on landing day.