Opportunity's twin rover, Spirit, began working on Mars three weeks before Opportunity. However, NASA said Spirit has been out of communication since March 22. If it awakens from hibernation and resumes communication, that rover will attain the Martian surface longevity record. Spirit's hibernation was anticipated, based on energy forecasts, as the amount of sunshine hitting the robot's solar panels declined during autumn on Mars' southern hemisphere.
The rovers' fourth winter solstice, the day of the Martian year with the least sunshine at their locations, was Wednesday, May 12, NASA said.
"Opportunity, and likely Spirit, surpassing the Viking Lander 1 longevity record is truly remarkable, considering these rovers were designed for only a 90-day mission on the surface of Mars," said John Callas, Mars Exploration Project Manager at NASA's Jet Propulsion Laboratory. "Passing the solstice means we're over the hump for the cold, dark, winter season."
NASA said science discoveries by the rovers have included Opportunity finding the first mineralogical evidence that Mars had liquid water and Spirit finding evidence for hot springs or steam vents and a past environment of explosive volcanism.