The Martian rover Spirit is adding a little mystery to its make-up after it did not report some of its activities on Jan. 21. The rover is now rolling along as planned, but what it did in those missing moments is still not known by the Spirit team at Jet Propulsion Laboratory.
Both rovers, Spirit and Opportunity, have recently celebrated five years on Mars, far surpassing their original 90 Martian day mission. It was on Spirit’s 1800th Martian day, or sol, when it radioed that it had received the day’s driving command, but it hadn’t moved. That was not unusual; Spirit may have sensed it was not ready to drive or it may not have been in the right position with the Sun to get its solar power.
“The rover didn’t move, it showed it had a drive error,” said John Callas, rover program manager.
He explained that the rovers take naps during the day, then wake up to follow commands.
“During its wake-up time it was supposed to drive,” he said. “We see it woke up and went to sleep an hour later.”
Not only did Spirit remain still but apparently it didn’t record any of its daily activities into the non-volatile memory. This is part of the rover’s memory that remains intact after the power is off. In the days that followed, rover controllers sent a command to Spirit to find the Sun with its camera. Spirit reported that it had followed the commands and found the Sun but not in its expected location. The JPL team is not certain why Spirit was dazed and confused.
“It was like it was sleepwalking,” said Callas.
But on Saturday, Spirit was back driving as it traversed about 30 centimeters (one foot). The rover team had commanded a longer drive but the rover stopped short after its right front wheel, which has been broken for a while, struck buried rock. Commands were sent for another drive on Monday in a different direction, avoiding the rock.
Spirit continues to follow commands and engineers are still going over information on why the rover took some time off.
Both Spirit and Opportunity have faced power failure and injuries but they continue to explore.
“We are just happy it keeps going,” Callas said.