NASA's Spirit rover stopped transmitting data from the surface of Mars for more than 24 hours, mission members said Thursday.
NASA last heard from Spirit early Wednesday. Since then, it has returned just random, meaningless data — and only then sporadically, scientists said. Initially, the scientists said they believed weather problems on Earth caused the glitch. They now said they believe the rover was experiencing hardware or software problems.
"This is a serious problem. This is an extremely serious anomaly," project manager Pete Theisinger said.
Spirit is one half of a $820 million mission. Its twin, Opportunity, is scheduled to land on Mars on Saturday.
After two days having trouble sending transmissions, the Mars rover Spirit sent data Friday morning to its NASA flight team in a communications session lasting 20 minutes, the agency's Jet Propulsion Laboratory said.
"The spacecraft sent limited data in a proper response to a ground command, and we're planning for commanding further communication sessions later today," Mars Exploration Rover Project Manager Pete Theisinger said.
NASA reported transmissions were detected at a NASA antenna complex near Madrid, Spain.
The Spirit rover stopped transmitting data from Mars on Wednesday, but mission controllers remained hopeful about reestablishing a connection, saying there were signs the craft was operating at a basic level.
Their efforts at restoring communications with Spirit come at a time when they are also focusing on a safe landing for the rover's twin, the Opportunity, set to descend on the other side of red planet. Opportunity was on course to land in a region called Meridiani Planum at 6:05 p.m. ET on January 24, NASA said.
Since Wednesday, NASA scientists had received a basic communication tone from the Spirit rover indicating it was alive, but the solid flows of data that marked its first 18 days on Mars stopped, said deputy project manager Richard Cook.
The tone is programmed into the spacecraft, to be emitted when there is a serious problem onboard.
"We know that we have had a very serious anomaly on the vehicle," said Pete Theisinger, manager of the $400 million Spirit mission, told reporters Thursday.
"Our ability to determine exactly what has happened has been limited by our inability to receive telemetry from the vehicle."