Nasa has lost contact with the US robotic probe on Mars, Spirit, because of a serious breakdown, space agency officials said Thursday.
"We have a very serious anomaly on the vehicle," said Pete Theisinger, project manager for the Mars Exploration Rover mission.
The National Aeronautics and Space Administration said Wednesday that thunder and lightning storms over Australia had prevented scientists from sending Spirit its daily instructions.
But experts now think a more serious problem caused the blackout.
Spirit arrived on Mars January 3 and started searching for signs of past life on the red planet last week.
Its twin rover, Opportunity, was due to touch down overnight January 24-25. The 820 million dollar mission expects each solar powered robot to keep working for about three months.