NASA's Mars Opportunity rover prepares for a 5th winter on Mars

NASA's Mars Opportunity rover prepares for a 5th winter on Mars.

NASA's lone surviving Mars rover has been busy exploring its surroundings since it rolled up to its latest crater destination four months ago. Now the solar-powered, six-wheel Opportunity is in search of a place to hunker down for the winter.

The robot geologist has been scouting out sites along the crater rim that not only have interesting rocks to examine but also ample sunshine. The hardy rover survived four previous Martian winters. Scientists expect no different and even drew up a to-do list.

Opportunity will "keep active all winter long," said Bruce Banerdt, rover project scientist at NASA headquarters.

Among its chores: studying bedrock and soil at its chosen winter site. While Opportunity can drive short distances from one outcrop to another, it can't venture far in the cold.

It's a bittersweet juncture for Opportunity, which along with its twin, Spirit, landed on opposite sides of the red planet in January 2004. Both operated beyond their original three-month mission and found geologic evidence that Mars was warmer and wetter than it is today.