In the risk-taking spirit of its human pioneer forebears, the Mars rover Opportunity is about to plunge into a crater from which it may never return.

NASA's Mars rover program has been so phenomenally successful over the past 3 1/2 years, with both rovers surviving years beyond their original mission profiles, that the space agency has decided to risk half the fleet by sending one of the robot explorers into a steep crater.

Opportunity is preparing to crawl over the lip of Victoria crater, a deep divot in the bleak Martian plains, in the hope that it will survive to plumb the geological history that's written into the crater walls.

"The rovers are getting older," said one mission leader. "It's kinda like sending your grandmother down the steep slope. You think she can make it, but you're a little concerned she might slip and fall and injure herself."

Click here for more. And here's some video about the decision.

You can see MArs with your own eyes if skies are clear and you're willing to step outside in the wee hours of the morning. The red planet is rising in the southeast this week just before 2 a.m. Tomorrow, the 4th, marks the winter solstice on Mars.

For more stellar fireworks in the sky, check this out. It's the latest from the Hubble Space Telescope.