USA: Only a faint beeping tone could be heard from America's Mars Spirit rover last night after the contraption suffered an "extremely serious anomaly", scientists said.
Spirit has performed almost flawlessly since landing on January 3rd, transmitting graphic images of the red planet back to Earth.
But NASA scientists said last night that the six-wheeled rover had sent no useful data back to Earth for 24 hours. All that can be heard from space is a faint beep, which signifies a major problem on board.
Scientists initially thought weather problems on Earth caused the glitch. But now they believe the rover may be suffering problems with its computer software or hardware.
Project manager Mr Pete Theisinger said: "This is a serious problem. This is an extremely serious anomaly." NASA last heard from Spirit as it prepared to continue examining a rock, just a few yards from its lander.
Spirit was in the process of grinding away at a tiny area of the weathered face of a sharply angled rock dubbed Adirondack.
The craft was searching Gusev Crater, a rock-strewn stretch of dusty, streaked soil which scientists believe may be the bed of an ancient lake.
If Mars once had surface water, it had the potential to support life.
Examination of the rock beneath the planet's surface could offer clues to the history of Mars.
An orbiting satellite, the Mars Global Surveyor, will attempt to communicate with the Spirit, when it passes over its location at around 4 a.m. GMT today.
Meanwhile, NASA scientists were desperately scanning data previously-sent by the Spirit in a bid to pinpoint the problem. Spirit is one half of a €445 million, three-month mission.
Its twin, Opportunity, is scheduled to land on Mars on Saturday.