On sol 133 of its mission Spirit drove about 371 feet (113 meters) on its own, more than 100 feet farther than its previous record, 256 feet (78 meters). The long drive was possible partly because of a two-day break in activity due to a software fault that popped up on sol 131.

While quickly remedied, the hiccup left rover planners unsure of Spirit's final position, which they spent sol 132 reacquiring using the rover's onboard cameras. The pause in driving activity gave Spirit a chance to charge up its batteries, preparing the robot for the longest drive in its history on Mars.

That software glitch appears to have occurred during a vulnerable three-microsecond period, when Spirit's computer attempted to perform a "write" command over a "write-protected" part of its RAM memory. According to Spirit's flight software team, the chances of the glitch occurring again are extremely low and no modifications to the planning process were needed to avoid the possibility in the future. The Opportunity rover, Spirit's twin, is vulnerable to the same software fault, they added.

Now in excellent health, Spirit has driven a total of 1.53 miles (2,473 meters) on Mars and is about half a mile (780 meters) away from the "Columbia Hills."

Opportunity Takes Time to Recharge

At "Endurance Crater," the Opportunity rover took some time of its own to rest up and recharge.

A 131-foot (40-meter) drive along the southern edge of Endurance on sol 111, along with an error in a Deep Space Network command transmission a day later, left Opportunity with little power left in its batteries.

The sol 111 drive carried Opportunity along an eight-degree slope that tilted the rover away from the Sun limiting the amount of sunlight its solar panels could draw upon. To make up for that power drain, Opportunity's handlers devised a restful plan for sol 112, canceling all but one of three planned UHF communication sessions. But a configuration error in the Deep Space Network prevented that plan from reaching Opportunity, so the rover went about its pre-scheduled remote sensing and communication activities for sol 112.

The rover did get some shuteye on sol 113, which flight controllers set aside for rover sleep and recharging. The following day saw a limited schedule of remote sensing activities, but mission planners expect Opportunity to take it easy as it approaches the rim of "Endurance" and a new position for a panoramic image session.