Nail-biting time for NASA as it awaits word from Mars

The $165 million Mars Polar Lander reached the surface of the Red Planet last night, but in the absence of a reassuring call home its controllers had no way of knowing whether the satellite had landed in one piece. The Mars Polar Lander, MPL, was sent on its 470 million-mile journey by the US National Aeronautics and Space Administration for a landing near the Martian south pole. The mission is to establish whether water exists in any form on the planet.

Late last night, however, the controllers, based at the Jet Propulsion Laboratory in Pasadena, California, had no answer for that question, nor for a more fundamental one - had the MPL landed safely.

The probe was dispatched 11 months ago and was to have landed at about 8.15 p.m. yesterday.

The MPL also carried two mini probes called Deep Space 2 which were to have left the mother craft for a kamikaze mission, crashing into the surface at speed. They were to have ended up about a metre deep in Martian soil in the hope that frozen water might be found in the underlying soil.

MPL's controllers knew they had an anxious 30-minute wait for the first word from the spacecraft. It should have reported its safe arrival, but as the minutes ticked by the looks of concern were obvious on the faces of JPL staff. Last September, NASA had a disastrous failure with MPL's sister ship, the Mars Polar Orbiter, after a miscalculation caused the spacecraft to smash into the surface.

The JPL team have plenty of options, however. The MPL has enough computing power to begin its mission on its own, scooping up Martian soil and baking it to check for water.

It has back-up systems that will allow it to operate for six days without contact with JPL and even then can switch to alternative systems and pursue its work. JPL will continue to attempt to lock onto MPL's radio signal - if it is sending one - so it could be some time before NASA knows whether the mission is a success, or a second spectacular failure.

If MPL wakes up, humankind will, for the first time, hear what it sounds like on the surface of Mars. The audio feed will be played back over the Internet at http://planetary.org