The little Martian rovers could continue to roll along the planet's surface 1,000 Martian days after their first landing.
Spirit and Opportunity were originally planned for a 90-Martian day mission. (A day on Mars is 24 hours, 39 minutes, 35 seconds.) Spirit reached its 1,000-day anniversary on Oct. 25, Opportunity will reach that goal on Nov. 15.
"We knew if we got through the first Martian winters it would last until something broke," said John Callus, rover project manager at JPL.
The Martian spring weather actually helped the rovers' longevity. Wind gusts blew dust off their power panels, allowing them to recharge.
Both rovers continue to explore even though they are showing signs of age. Spirit's right front wheel no longer works; it travels on five wheels now. A joint of Opportunity's arm has degraded. Engineers stow the arm while it travels in order to protect it from harm.
"It's like having your arm in a cast. You might be able to drive, but not play tennis," Callus said.
Opportunity is now on the rim of Victoria crater, Spirit has climbed over the Columbia hills and is descending into the inner basin.
Callus realizes that there will come a day when the rovers no longer answer their calls.
"It will be a sad day when we have to say goodbye but we will remember all that they have done," Callus said.
