Mars rovers still going strong after a year of exploring
BY SPACEFLIGHT NOW
Posted: January 3, 2005
The remarkably inexhaustible Mars rovers, built to explore opposite sides of the Red Planet for three months in early 2004 and uncover proof of past water on Earth's neighbor, are still trucking along to the amazement and delight of scientists one year after the adventure began.
Opportunity quickly found evidence that standing water once covered its landing site, answering a fundamental question about the Red Planet. Later, Spirit successfully found water clues at its locale, too.
As the months flew past, both rovers continued to roll and their missions were extended. The 90-day warranties were surpassed as the vehicles racked up greater distances on their odometers. Today, Spirit and Opportunity remain hard a work. And not even the rovers' lead scientist, Steve Squyres of Cornell University, thought the craft would last this long.
"No, and I had pretty wild dreams for them. I thought maybe they would go four or five months, maybe six, and over their entire lifetime they might drive a thousand yards, something like that," he said Monday.
"But three, four kilometers, a year of operation, climbing mountains, no, I would never have guessed it."
To date, Spirit has driven over four kilometers as it traveled from its landing site to the rim of Bonneville Crater and is now ascending Husband Hill, named for the fallen commander of space shuttle Columbia. Opportunity has rolled two kilometers and spent much of its time inside the small Eagle Crater in which is landed and the stadium-sized Endurance Crater. The rovers have beamed 86 gigabits of data and 62,000 pictures to Earth, said Jim Erickson, the project manager at NASA's Jet Propulsion Laboratory.
"With Opportunity we have these flat plains extending off to the south and then two miles away we have this fantastically complicated 'badlands' kind of topography. We call it the etched terrain but we really don't know what it is. We're going to go down there and explore the rocks there and they are going to tell us, I think, something very new and different compared to anything we've seen so far."
While discoveries are still being made, the legacy of the Mars rovers achieved so far is showing the planet had an environment for life.
"I think the most important single finding from the mission is Mars at one time in one place on the surface had conditions that probably would have been suitable for supporting life. That doesn't say life was there. What we can say is Mars was a habitable world. Whether it was inhabited is a totally different question. But now we know where to go and look," Squyres said.
"The thing that really makes me most interested now, the thing that really gets me going when I think about what we have learned, is whether or not the rocks -- especially where Opportunity landed -- could preserve evidence of what might have been in that water. We've got compelling evidence that water was there, that it was a habitable environment, so forth and so on, but was there something living there? The thing that is beautiful about these rocks is that they are the kind of rocks that are very good at preserving microscopic fossils. So if we could actually get some of these materials and get them back to Earth, then we might be able to try and answer that question."
But such a sample return mission won't happen before the next decade. NASA plans to launch a sophisticated orbiter to snap highly detailed pictures of the Martian surface in August, a lander with a digging arm to probe water ice near the north pole in 2007 and a nuclear-powered science rover in 2009.
The continuing studies by Spirit and Opportunity are aimed at gathering more detail on what the environment was like on Mars.
"We're recently getting clues that it was actually a pretty arid environment. It was dry much of the time and then there would be these occasional inundations of water. So it was an alternating wet and dry kind of climate. We've also been getting increasing clues that the water may have been very acidic; it may have been sort of sulfuric acid as opposed to nice, clear drinking water. So we're getting more and more detail on what the environment was like with each passing month," Squyres said.
Life can be found in highly acidic water on Earth today, he said.
"So these kinds of environments are certainly capable of supporting life. Whether life could first take hold in a place like that is something that we really don't know."
"They are in remarkably good shape. With Spirit we had a little issue with the right front wheel for a while where it was taking more electrical current to turn it than it used to. We think that was because of a problem with the lubricants, the grease in the gear box. But with time and by applying a little bit of heat we've actually been able to spread that grease around a little bit and that wheel has actually gotten better. So right now these two vehicles are dirty, they're scratched up, but they are still going and are in very good shape," Squyres said.
Both rovers weathered the worst of wintertime and reduced solar power, but now spring is approaching.
"We survived the winter. That is the key thing -- we survived the winter. The sun is coming back towards us; the power is going up. The thing we have to worry about though, we've got weather to worry about. What's happening is we're starting to see little dust storms. Not big ones, not big global ones, not something that threatens the lives of the rovers, but we've begun to see recently in the last week or two evidence of little local storms. So we're actually tracking weather systems on Mars to keep track of how it's going to affect the vehicles."
Rover project manager Erickson says the level dust accumulation on the vehicles' power-generating solar arrays is less than engineers expected and the frigid temperatures that take their toll on the craft have been less severe than predicted.
"The rovers have been lucky so far. The power situation, which is rosy, wasn't what we expected. The solar panels turned out to be staying much cleaner than we planned on. And the overnight temperature lows that we've been seeing are much less than we planned for. We were ready to accept much colder temperatures. But it's all to the good, it means we're able to continue on and we're in a strong position to continue exploration with both of the rovers. Bad things could happen to us at any time. Random part failures could lose the missions tomorrow. But as long as we have them, we're going to keep using them to the best of their ability."
"It costs about $3 million a month to keep the rovers going. It seems inconceivable to me that if the missions are still producing good science that we will not find a way to keep them going. We will manage somehow," said Firouz Naderi, manager of NASA's Mars Exploration Program at JPL.
Engineers acknowledge there are countless scenarios that would stop the craft dead in their tracks. No one knows if either rover will survive another couple of months.
"It depends on what kills them," Squyres said.
"One of the things that could do it is dust buildup on the solar arrays. The solar arrays...are pretty clean right now, especially on Opportunity. So if it is that, they could last for many months longer. But there are other things that could do it too. We have a lot of moving parts on these vehicles -- there's lots of motors, lots of gear boxes, lots of things that can wear out. If that starts to happen, then it will be an issue. The other possibility is the electronics. There are a lot of electrical parts in these things that if they fail -- bam! -- that's it, the rover wouldn't wake up the next morning.
"So we try to plan for many months of operations but on each individual day we try to drive them literally like there's no tomorrow."
Squyres said Monday that Spirit and Opportunity have provided the "adventure of a lifetime" and proved a prediction he made last January after the landings that scientists were about to embark on "the coolest geology field trip in human history."
"The thing about exploration is you never know what is over that next hill, you never know what is going to come next. These rovers still have a lot of capability left in them. We are pushing them very hard, we're pushing ourselves very hard and we'll see what Mars has to show us."
But the reality is the rovers won't last forever.
"It is going to be a hard day. You grow very attached to them. They've developed their own personalities, they are pieces of machinery that we really care about and when we lose them it is going to be a rough day. But they will have died honorable deaths, when it does happen. They have achieved far more than any of us expected. It will be sad but in its own way satisfying," Squyres said.