NASA's Mars rover Spirit is suffering a new bout of amnesia, one that comes after months of being stuck in deep Martian sand.

The 6-year-old rover's latest memory lapse occurred Oct. 24 and came more than six months after a series of four other amnesia events earlier this year. During the events, the plucky rover failed to record science observations in the part of its flash computer memory that stores information overnight when other systems are powered down.

"We still don't have information about what causes these amnesia events," said rover project manager John Callas at NASA's Jet Propulsion Laboratory, Pasadena, Calif., in an update.

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In the latest event, Spirit did not use its flash memory between Oct. 24 and Oct. 27. The rover does have an alternate memory system in which to store data, but must beam that information home to Earth before entering an overnight sleep period, mission managers said.

Callas said engineers are weighing Spirit's amnesia problem to determine how it may affect day-to-day operations for the long term. Aside from the memory glitch, the rover is in good health and communicating with Earth.

"If they are intermittent and infrequent, they are a nuisance that would set us back a day or two when they occur. If the condition becomes persistent or frequent, we will need to go to an alternate strategy that avoids depending on flash memory," Callas said. "We would only get data collected the same day and any unsent data from an earlier day would be lost. The total volume of data returned by the rover is expected to be about the same."

Meanwhile, the new memory lapses will likely further delay NASA's efforts to extricate Spirit from its Martian sand trap. The rover has been mired in deep sand since April, unable to move.

An independent team of robotics experts is currently reviewing recent NASA tests that used a ground-based version of Spirit to come up with escape plan for the stuck rover on Mars. NASA has mounted a "Free Spirit" campaign to come up with ways to free its beloved rover.
NASA launched Spirit and its robotic twin Opportunity in 2003 on a mission to explore Mars. The rovers landed in different parts of the planet in January 2004 and spent more than five years roving across Mars and uncovering clues to the planet's watery past.

While engineers try to free Spirit, its robotic twin Opportunity is headed toward a giant Martian crater called Endeavour. Earlier this month, Opportunity spotted a Martian meteorite dubbed Shelter Island on the heels of another space rock find — called Block Island — in September. The rover used its onboard instruments to study both meteorites.

Initially built for a 90-day mission, the two rovers have received repeated life extensions. Spirit is the older of the two rovers and has spent five years and nine months exploring Mars.