The worst of Mars’ southern hemisphere winter has passed. Opportunity has roused from her winter slumber, and she’s doing what a Mars Exploration Rover should be doing: rolling across Mars!

Winter is tough on a solar-powered rover. Opportunity’s sister, Spirit, died during the previous Martian winter, nearly two Earth years ago. Just like on Earth, the Sun comes in at a shallower angle, rises later, and sets earlier, reducing the amount of light that Opportunity’s bat-wing solar panels can catch.

Mars’ southern hemisphere winters are especially hard, because Mars’ elliptical orbit takes it particularly far from the Sun when it’s winter in the southern hemisphere. That makes it even colder than it would otherwise be. I explain more about Mars’ extreme seasons in this video:

You might think a rover doesn’t care about the cold, but Opportunity has to warm up her wheel motors before she can run them. The colder it is, the more power it takes for heat, and the less available to rove or do science.

It doesn’t help that in Opportunity’s eight-plus years on Mars (eight! This from a rover warranted to last only three months), she’s accumulated a fair amount of dust on her solar panels, screening out half the available sunlight. The net result of all of this: Opportunity stood still for six months, from December 5 until May 7, just waiting out the winter.

The waiting’s over, and Oppy’s on the road again. (Aside: as a kid, “Oppy” was what I called Optimus Prime. Now, I’ve transferred the pet name to a real autonomous robot.) Click to enlarge and take in this 360-degree panoramic view of Opportunity’s most recent position. I can’t tell you how happy I am to see fresh wheel tracks in the sand.

Opportunity stopped after driving away from her winter haven in late May, 2012, to take in a 350-degree view. Tracks lead back to her winter parking spot.

The wheel tracks lead straight back to her overwintering spot. In the foreground, you might notice some white veins of rock poking up above the ground. Those white veins are Martian gold, in the form of mineral deposits left behind in the fractured rock of the giant Endeavour crater’s rim by hot groundwater seeping through it a long time ago.  In those veins are clues to what Mars was like, way back when liquid water could flow on it, three or more billion years ago. Opportunity’s next task is to examine those veins up close with her cameras and elemental analyzer.

For more on Opportunity’s ongoing adventures, check out my blog for The Planetary Society. Also recommended are Stuart Atkinson’s blog “Road to Endeavour,” and if you want to discuss the latest pictures from Mars, visit the Opportunity discussion forum at unmannedspaceflight.com, where I’m an administrator.