Specifically, Spirit and Opportunity.
Spirit made a successful landing on January 4th, 2004, and Opportunity landed January 25th. So far, Opportunity has been functioning 25 times longer than originally planned. It is currently heading for the Endeavor crater.
(Opportunity. SOURCE)
Both rovers discovered evidence that could indicate water used to be on Mars. Spirit found crystallized minerals in magma, possibly dissolved by water, along with a high concentration of salt in the soil. Opportunity found bedrock formations that form because of a current, along with hydroxide ions in jarosite, which could mean the mineral formed in the presence of water.
(Spirit's first image. SOURCE)
Hopefully, Spirit will communicate again with Earth and begin exploring Mars again. But even if it doesn't--it went far beyond its expected time--the rover made some important discoveries, as did its twin.
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Do you think there's a chance Spirit will come out of hibernation?
-----The Golden Eagle