This full-circle view from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Spirit shows the terrain surrounding the location called "Troy," where Spirit became embedded in soft soil during the spring of 2009.

NASA?s Marsrover Spirit is suffering a new bout of amnesia, one that comes after months ofbeing stuck in deep Martian sand.

The6-year-old rover?s latestmemory lapse occurred Oct. 24 and came more than six months after a seriesof four other amnesia events earlier this year. During the events, theplucky rover failed to record science observations in the part of its flashcomputer memory that stores information overnight when other systems arepowered down.

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

In thelatest 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 mustbeam that information home to Earth before entering an overnight sleep period,mission managers said.

Callas saidengineers are weighing Spirit?s amnesia problem to determine how it may affectday-to-day operations for the long term. Aside from the memory glitch, the rover is in good health andcommunicating with Earth.

?If theyare intermittent and infrequent, they are a nuisance that would set us back aday or two when they occur. If the condition becomes persistent or frequent, wewill 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 datafrom an earlier day would be lost. The total volume of data returned by therover is expected to be about the same."

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

Anindependent team of robotics experts is currently reviewing recent NASA teststhat used a ground-based version of Spirit to come up with escape plan for thestuck rover on Mars. NASA has mounted a ?Free Spirit? campaign to come up withways to free its beloved rover.

NASA launchedSpirit and its robotictwin Opportunity in 2003 on a mission to explore Mars. The rovers landed indifferent parts of the planet in January 2004 and spent more than five yearsroving across Mars and uncovering clues to the planet?s watery past.

Whileengineers try to free Spirit, its robotic twin Opportunity is headed toward agiant Martian crater called Endeavour. Earlier this month, Opportunity spotteda Martian meteorite dubbed Shelter Island on the heels of another spacerock find ? called Block Island ? in September. The rover used its onboardinstruments to study both meteorites.

Initiallybuilt for a 90-day mission, the two rovers have received repeated lifeextensions. Spirit is the older of the two rovers and has spent five years andnine months exploring Mars.