"The first problem, unfortunately, is distance. According to NASA's Mars map, the Curiosity and Opportunity sites are about 5,200 miles (8,400 km) apart from one another. Curiosity's a bit swifter-footed than Opportunity, but even so, the young sprite would just take way too long to cover that terrain. To navigate the Martian terrain, these rovers require constant guidance from Earth Combined with the long delay between message transmission and receipt, even a trek of a few feet can take days.

The second problem is that Curiosity is an explorer, not a repair bot. It would be a monumental challenge to repurpose its onboard instruments to even clear dust off of Opportunity's solar panels. And there's no guarantee that's all that's gone wrong with the rover sitting silently in the Martian cold and darkness."