Nasa probe attempts perilous landing on Mars

US scientists were hoping to land a spacecraft near Mars's north pole - but say they not were not overly confident of success. Nasa's Jet Propulsion Laboratory in Pasadena, California, puts the odds on accomplishing the mission at less than 50 per cent.

The spacecraft, Phoenix, entered the Martian atmosphere last night at about 13,000 miles per hour. It was then expected to rely on its thermal shield, then a parachute and thrusters to slow down to a mere eight kilometres per hour before touchdown.

Its destination is the polar region known as Vastitas Borealis, in a similar location to northern Canada on Earth. If all goes according to plan, Phoenix will become the first spacecraft to land in the Martian arctic. It will spend the next three months searching for signs of life.

The result of the landing was expected to be known at 4.53 p.m. Pacific time (2353 GMT), around 15 minutes after the probe makes contact with Mars's surface, because radio signals take that much time to travel the 275 million kilometres) to Earth, Nasa said.

The distance between Earth and Mars varies. At their closest they are about 100 million kilometres apart, while at their most distant they are about 380 million kilometres apart.

In the past 50 years about half of the three dozen spacecraft sent to Mars have crashed, disappeared or missed the planet altogether.