NASA's twin Mars rovers, Spirit and Opportunity, have been on the surface of Mars for more than eight years.
NASA's Mars rover Spirit may be dead, but it is far from forgotten.
The golf-cart-size robot hasn't communicated with Earth since March 2010, and NASA announced Tuesday (May 24) that it will stop sending daily wake-up calls to Spirit. The cause of death appears to be hypothermia; extreme cold likely damaged the rover's electronics after it lost power during the Martian winter of 2009-2010.
Spirit lived a long, full and extremely productive life. The rover landed with its twin, Opportunity, on the Martian surface in January 2004 on a three-month mission to search for signs of past water activity on Mars. Both robots delivered in a big way, finding lots of evidence that the Red Planet was once a much wetter, warmer place. [Mars Photos by Spirit and Opportunity]
Spirit outlived its warranty by about six years, and Opportunity is still going strong.
SPACE.com recently caught up with Steve Squyres, lead scientist for Spirit and Opportunity's mission and an astronomy professor at Cornell University. In an email interview, Squyres talked about Spirit's accomplishments, its legacy and what the rover's death means to him:
SPACE.com: When, and how, did you find out that all hope for Spirit's recovery was lost?
Steve Squyres: Well, it's been a gradual realization. Our best hope for hearing from Spirit was last fall. When that didn't happen, we began a long, careful process of trying every possible approach to re-establishing contact. But it slowly became clear that it was unlikely, and I personally got used to the idea that Spirit's mission was probably over several months ago. [Video: RIP Spirit: Six Years of Mars Science]
SPACE.com: How do you feel about Spirit's passing?
Squyres: It actually feels a lot better than I expected it to feel. It's very sad to lose Spirit, of course. But two things have softened the blow. First, as I said, we've had a long time to get used to the idea. And second, even though Spirit is dead, she died an honorable death.
If we'd lost her early in the mission, before she accomplished so much, it would have been much harder. But she accomplished so much more than any of us expected; the sadness is very much tempered with satisfaction and pride.
SPACE.com: Will you and the other science team members have any kind of ceremony to mark Spirit's "death?"
Squyres: Yes. We're planning to have a sort of "Irish wake" for Spirit, involving the whole mission team, at JPL [NASA's Jet Propulsion Laboratory] in July. [Mars: The Spacecraft Graveyard]
SPACE.com: What, in your view, are Spirit's most important discoveries?
Squyres: It's hard for me to say, of course; I'm a little too close to it. But my first reaction would be to say that the big ones are the silica deposits at Home Plate, the carbonates at Comanche and all the evidence for hydrothermal systems and explosive volcanism.
What we've learned is that early Mars at Spirit's site was a hot, violent place, with hot springs, steam vents and volcanic explosions. It was extraordinarily different from the Mars of today.
SPACE.com: What is your favorite memory of Spirit?
Squyres: Before we launched, Spirit was always our "problem child." We built her first, which means she went through almost every test before Opportunity did. And the first time you run a test, things usually don't work. So we learned a lot with Spirit!
Once we got to Mars, I think my most vivid memories are of the first winter. I never expected Spirit to survive even one winter on Mars; her landing site was just too far from the equator, and the winters were too harsh. But by the time winter came on, we were already in the Columbia Hills. Spirit survived that winter by working up the steep north face of Husband Hill, tilting her solar arrays toward the sun and keeping the power levels up.
A rover we never expected to survive a Martian winter spent her first winter not just surviving, but doing the first mountaineering on another planet — with spectacular scientific results. It was remarkable.
SPACE.com: What will Spirit's legacy be? How will the rover be remembered?
Squyres: Part of it, of course, will be the science. Our picture of what Mars was once like is now dramatically clearer and more vivid because of what we've learned from Spirit. But the other part, I hope, will be the inspiration that people, especially kids, will take away from Spirit's mission.
I have had long, thoughtful conversations about Spirit with kids who have had a rover on Mars as long as they can remember. And my fondest hope for Spirit is that somewhere there are kids who will look at what we did with her and say to themselves, "Well, that's pretty cool, but I bet when I grow up I can do better." That's what we need for the future of space exploration.
SPACE.com: How is Opportunity doing?
Squyres: Opportunity's doing fine. We've got a few minor mechanical problems — the right front steering actuator, and azimuth actuator at the shoulder of the arm. But we've been dealing with these issues for years, and the rover is in good health and driving steadily.
Right now Opportunity is heading at high speed for the rim of Endeavour Crater, and if all goes well she should be there in not too many more months.
SPACE.com: Spirit and Opportunity far outlasted their planned lifetimes and accomplished so much. Have they raised the bar too high for future rovers?
Squyres: I certainly hope so! [Vote Now: Where Should NASA's Next Mars Rover Land?]
SPACE.com: Is there anything else you'd like to say to commemorate Spirit, the work it did or the people who made it all possible?
Squyres: The key thing is the people. This story is very much about Spirit, of course.
But in the end, Spirit existed, and did what she did, because of the extraordinary team of engineers and scientists who worked so hard to make it possible. It's a team that I'm incredibly proud to have been a small part of. Working with them has been quite literally the adventure of a lifetime.