Five years ago, Spirit and Opportunity landed on Mars. While they're getting pretty broken down and rickety, they're still functioning despite their expected lifetime of a few months. This is an amazing testament to these vehicles roaming around another planet and to the people here on earth controlling and maintaining them.
I watched a TV special on the rovers, and it ended with surprising poignancy. I thought it was very touching that these normally down-to-earth scientists and technicians were speaking about the rovers very personably, as if they were more like beloved pets. It made me a little emotional myself.
The show ended with this dialog:
Ashley Stroupe: These rovers are pretty old, now. They're getting kind of arthritic; they don't see so well any more because the cameras are getting more and more coated with dust so their vision's getting a little fuzzy.
Together, they've explored Mars in a way that no planet other than earth has ever been explored. And those who work with them have given up trying to predict when their mission will finally end.
Steve Squyres: They're gonna die when they die. You know, at this point, every day's a gift. We just push the vehicles as hard as we can, enjoy them while we've got them, and some day they're gonna die and I don't know when.
However this adventure ends, their legacy is assured. They've returned hundreds of thousands of images, enough data on martian water history to keep scientists busy for decades. And their most important work may be yet to come.
I used to have this naïve idea that at some point we'd be able to sit back and fold our arms and say "yeah, well we did it. We learned everything we can about Mars with these rovers." I don't think that's going to happen.
But then, there are scenarios in which the rover is still alive, but it can't do much useful science any more. And you'd like to think at that point, well, you turn it off. Well, you can't turn them off. They don't have an off switch. If you build a piece of hardware with an off switch you might accidentally hit that off switch when you don't mean to, and you don't want to do that. So we have no way to turn them off. There's not a command that we can send that says, okay, *click*, you're done.
And so, as long as the rovers are alive, they'll wake up every morning when the sun hits their solar panels. And they'll call home and await instructions, whether anyone is listening or not.
And long after their circuit boards have given out, they'll be sitting on the surface of a planet where little has changed for billions of years.
It's cold, it's dry, there's no vegetation, they're not going to rust or anything like that. You know, these things could be still sitting there with their aluminum surfaces still shiny a million years from now. They're going to last a long long time. Longer than most things that humans have ever built.