"NARRATOR:" "It began as a three-month mission to Mars." "[cheering] lt's turned into one of the greatest adventures of the Space Age." "MAN:" "Oh, my God!" "NARRATOR: exploring an alien world through the eyes of two rovers 100 million miles away." "MAN:" "There's something just absolutely magical about that." "It is like being there!" "NARRATOR:" "Now one rover is in serious trouble, but it's not dead yet." "MAN:" "Betting against the rovers is a good way to lose money." "I don't do it." "NARRATOR:" "Spirit and Opportunity... five years later... still living on Mars." "NARRATOR:" "For more than five years, sunrise on Mars has sent current flowing through the solar panels of the rover named Opportunity, waking it up for another day of work." "At the same moment, on the other side of the planet, the setting sun has marked the end of the day for the rover Spirit and the beginning of another long, cold night." "But now Spirit is in trouble, stuck in quicksand and facing yet another brush with death on Mars." "STEVE SQUYRES:" "You never know when these things are going to drop dead." "You know, they could last another three years, they could die tomorrow." "They could be dead right now and we just haven't gotten the downlink that shows it yet." "NARRATOR:" "This is not the first time a rover has gotten in trouble on Mars." "It's just one of many potential disasters the two explorers have faced and survived during their epic overland expedition." "So far they've been tougher, more resilient, and luckier than anyone could have hoped." "They were expected to last just 90 Martian days, called sols... so the scientists and the rover engineers at NASA's Jet propulsion Lab in pasadena, California, have approached each sol as if it might be the last." "SCOTT maxwell:" "We were impressed very early with the idea that the rovers were under a death sentence." "We knew that there was a kind of clock that was counting down and at the end of 90 sols, like that was all the time that we could count on that we were gonna get." "And we didn't even know if we'd get all that." "SQUYReS:" "I was pretty optimistic." "I thought we were going to get at least 1 50, maybe 180 sols." "Four plus years?" "No." "Not even close." "NARRATOR:" "Opportunity got off to a quick start, landing in January 2004, after a 7-month journey to Mars." "Touching down in a region called Meridiani planum, it bounced across the plain in its airbag cocoon." "By chance, it rolled into a shallow crater." "At jpl they waited for the first pictures... as Opportunity emerged from its protective shell." "[cheering]" "SQUYReS:" "We open our eyes and there's this astounding outcrop of layered bedrock right in front of the vehicle." "That outcrop in the distance is just is out of this world." "I can't wait to get there." "NARRATOR:" "Bedrock, with its geological clues to the history of ancient Mars, is what the rovers came looking for." "It could help answer the ultimate question in space science-- are we alone in the universe?" "The search for extraterrestrial life begins with liquid water, a fundamental necessity of life on earth." "Mars has been a frigid desert for billions of years, but satellite images suggest that liquid water once flowed across the surface." "From orbit, though, it's hard to tell whether it was an environment that could have supported life." "SQUYReS:" "How much water was there?" "What was its chemistry?" "Suppose you were a microbe, would you have liked that place or not?" "If so, why?" "NARRATOR:" "The rovers are field geologists, designed to read clues to the environment of early Mars preserved in the rocks and minerals." "each has a toolkit on its robotic arm to grind off the weathered surface of rocks and analyze their composition." "They see the world in three dimensions with four pairs of stereo cameras." "There's a high-resolution pancam... for color panoramas, collected and stitched together from individual frames." "Color filters enhance details invisible to human eyes... and an infrared spectrometer scans for minerals that may have formed in the presence of water." "They have wide-angle black-and-white stereo vision for navigation and planning." "And below the deck, fisheye cameras see the world at ground level, looking backward and forward." "Opportunity goes to work looking for evidence of ancient water, and over a few weeks makes a series of startling discoveries." "SQUYReS:" "It was like being inside this bizarre Martian mystery novel, where every sol or two you get a new clue handed to you." "NARRATOR:" "First come tiny spheres the size of BBs, littering the ground and embedded in the outcrop like blueberries in a muffin." "SQUYReS:" "It was such a surprise." "I mean, what the heck were those things?" "NARRATOR:" "The instruments find that they're made of an iron mineral called hematite." "On earth it forms spheres like these in water-soaked rocks, like pearls in oysters." "Then comes the discovery of sulfur-rich minerals, including one called jarosite that forms only in the presence of water." "And finally, evidence of ripples created by water flowing across the surface, frozen in time as the sand turned to stone." "The clues add up to a place where salty water, virtually sulfuric acid, once soaked the ground and sometimes flowed across the surface." "On earth, microbial life can thrive in places like this." "SQUYReS:" "There wasn't a single one of us who expected what we found." "Anybody who tells you so is lying." "It was a new Mars!" "We were giddy, we were incredulous, we were sleep deprived beyond words." "It was so tiring." "But we were just running on adrenaline, you know." "And it was just so much fun." "It was the most fun I've ever had as a scientist." "It was just fabulous." "NARRATOR:" "If Opportunity's mission had ended here it would have been a great success." "But now the rover heads for a bigger, deeper crater nearby, which could expose even more bedrock." "Unfortunately, on the other side of Mars, things have not gone so well." "Spirit landed three weeks ahead of Opportunity in Gusev Crater, a hundred-mile diameter basin that scientists believe once held a Martian lake." "But on the ground Spirit finds no evidence of water history." "every rock appears to be volcanic lava." "SQUYReS:" "I wouldn't have wanted to admit it at the time, but the Spirit landing site initially was a crushing disappointment." "We went there looking for layered sedimentary rocks laid down billions of years ago in a Martian lake, and instead we got lava as far as the eye could see." "every damn rock was like every other damn rock." "They were just all the same." "NARRATOR:" "If the evidence they're looking for has been buried, they might find it exposed in the walls of Bonneville Crater some 400 yards from the landing site." "But when Spirit finally pulls up to the rim two months after landing, there's nothing inside but more lava." "hap McSWeeN:" "We hoped for something a little more spectacular than this." "I'm gonna be surprised if we decide to drive down into the crater." "We might, but I don't know." "SQUYReS:" "Spirit was just seeing nothing but lava as far as the eye could see." "And the Spirit team got a little disheartened after a while." "NARRATOR: even so, many on Spirit's team embrace the role of the underdog." "SQUYReS: people just got emotionally attached to their rover." "You know, I'd tell them, well, you can switch to Opportunity, and they'd say no, no, I'm not gonna." "Because they had gotten their heart set on Spirit succeeding." "maxwell:" "Opportunity was certainly the lucky rover." "But for me I worked on Spirit, and Spirit is my favorite rover, because Spirit had to work for everything she ever got in her life." "NARRATOR:" "The best chance for Spirit to salvage its mission now is a mile and a half away in the Columbia Hills... a two-month journey, four times farther than the rover was ever expected to drive." "Squyres thinks it's the best option, but the engineers are dubious." "ROB manning:" "I remember he said that." "This is where we're going." "What do you mean, you're going to drive up on those hills?" "This is going to be a lot more than 90 days!" "Good luck." "We're probably going to die on the way there." "He said no, we're going to go." "I said OK." "You're driving." "You've got the keys." "Good luck." "SQUYReS:" "We're 100 sols into our 90-sol mission." "The warranty has expired." "Our only chance of getting to something new was to push the vehicle beyond anything it had ever been designed to handle." "Otherwise it was gonna be just lava until the end of the mission." "NARRATOR:" "While Spirit treks to the hills," "Opportunity pulls up to the rim of endurance Crater after a month-long drive across the plains of Meridiani." "SQUYReS: endurance Crater scared the hell out of me the first time I saw it." "It's the kind of place where if we screwed up, you know, a little rover could fall off a cliff and die." "NARRATOR:" "But it's also a potential gold mine for science, with lots of exposed bedrock down below." "SQUYReS:" "Oh, my God!" "NARRATOR:" "Now comes a decision." "Opportunity is already past the 90-sol mark and living on borrowed time." "If entering endurance turns out to be a one-way trip, it wouldn't be the worst place on Mars to be trapped." "But nobody wants to send the rover on a suicide mission." "SQUYReS:" "We all wanted to go in." "I mean, we're standing on the lip of the most magnificent thing anyone's ever seen on Mars, with a rover that we all believe in our hearts can do it." "everybody wanted to go into the crater, but you want to do it right." "NARRATOR:" "This is not an easy risk to calculate." "The rovers were designed to operate on flat ground." "No one knows how well they can climb." "manning:" "We never had to test it to its limit before." "All we had to do was test to the requirements." "We had to convince our management here and at NASA headquarters that we weren't going to damage this vehicle or get stuck." "MATT wallace:" "Frankly, if we can't climb pretty reliably up these rocks at 25 degrees, we're not going into this crater." "SQUYReS: everybody had to approve that decision." "If we did screw up, I didn't want somebody popping out of the woodwork and saying, well, you didn't ask me." "If you'd have asked me I would have said you can't go in." "No, I wanted to make sure that we were all holding hands when we jumped off the cliff together." "NARRATOR:" "They decide to run some tests, replicating the situation on Mars as closely as possible." "The crater wall appears to be closely spaced slabs of rock." "They simulate it as best they can with patio stones and sand." "Then they bring out the test rover to see what kind of slopes it can handle." "MAN: 1 5 up...10 down." "MAN:" "OK." "MAN:" "Come on, baby." "Come on, darling." "SQUYReS:" "And in fact, the thing climbed beautifully." "I was stunned by how well this thing could climb steep, steep slopes, as long as they were rocky." "30, 32 degrees, boop, boop, boop, right up it, it was amazing." "NARRATOR:" "In June 2004, with Opportunity's mission on the line," "NASA gives the go-ahead to enter endurance Crater." "Now its fate is in the hands of the drivers-- the privileged few at jpl who interact directly with the rovers, translating directions from the scientists into commands a robot can understand." "They spend their days immersed in a 3D, virtual reality environment created by the rovers' own cameras." "maxwell:" "It's one of the just amazing things about this, is the sense that you get of being there." "If you were standing at that spot on Mars right now, this is what you would see." "NARRATOR:" "It can take more than 20 minutes for radio signals sent from earth to reach Mars, so the rovers can't be driven in real time like remote control cars." "chris LeGeR:" "You really are programming the rover." "It's not a joystick." "It's OK, you know, go 10 meters forward, turn 5 degrees, you know, check for obstacles, measure your progress..." "NARRATOR:" "Typical speed is just yards per hour, but rover driving is always a white-knuckle experience." "julie TOWNSeND:" "Nobody has more anxiety every day about what's being done to the rovers." "It's the feeling that I sequenced all the commands that are going to move this rover today, and if something goes wrong, this is on me." "NARRATOR:" "After an eight-week, mile-and-a-half trek through a desert of broken lava," "Spirit finally reaches the Columbia Hills." "evidence of water may be on the upper slopes." "The summit is just 300 feet above the crater floor, but it's a monumental challenge for this rover." "maxwell:" "She's already driven three times as far as she's supposed to be able to drive and lived twice as long as she was supposed to live." "If you imagine you've driven your car 300,000 miles without taking it to a gas station and now you've got to climb Mount everest with it." "NARRATOR:" "Spirit's solar panels, its only source of energy, are getting dusty and producing just half as much power as they used to." "The right front wheel is drawing more current than it should, raising fears that it might fail soon." "But most ominous is the approach of the first Martian winter, which no one expects the rovers to survive." "SQUYReS:" "The seasons were changing." "Spirit is in the southern hemisphere of Mars." "And what that means is in the winter the sun is going to go low in the northern sky." "And it's going to get lower and lower and lower." "And as it gets lower, the amount of power that we're going to get from solar arrays is going to get less and less and less unless we can do something." "NARRATOR:" "They could solve the problem and possibly survive the winter by tilting the solar panels toward the sun to get more power." "SQUYReS:" "Well, we didn't build a tilt mechanism into the rover." "The only way to tilt them towards the sun is to tilt the whole rover towards the sun." "But the beauty of it was, now we had a hill." "NARRATOR:" "If they can find a route that keeps the solar panels tilted toward the sun," "Spirit might be able to survive the winter and climb the mountain at the same time." "With a new strategy for survival that the rover designers never envisioned," "Spirit sets off on a risky climb that may or may not pay off scientifically." "Inside endurance Crater, close to the Martian equator," "Opportunity thrives all winter." "Sampling rocks at deeper and deeper levels, the rover adds greater depth of time to the water story it found at the landing site." "SQUYReS:" "What endurance offers is a vertical view into Mars." "As we went deeper, the chemistry and the texture of the rocks changed dramatically in a way that indicated to us that the deeper rocks had been soaked in water for a long period of time." "NARRATOR:" "It now appears that the water at Meridiani may have lasted hundreds of thousands if not millions of years." "SQUYReS:" "The gamble to go into the crater definitely paid off scientifically." "It really, really improved our understanding of what we were dealing with here." "NARRATOR:" "It's been six months since Opportunity entered endurance Crater." "Now it's time to move on to something new." "It's a long way from endurance Crater to anything dramatically different." "The most obvious target lies six kilometers, almost four miles, to the south-- a huge impact crater called Victoria." "Deeper than endurance, it's a chance to look even farther back in time." "JOHN CALLAS:" "We thought wow, could we get there?" "Six kilometers to the south-- remember, that's six times the designed distance capability of the rover." "NARRATOR:" "The challenge is not only the distance, but the time it will take to get there, which could be hundreds of sols." "CALLAS: each day on Mars the temperature goes between maybe minus 100 degrees Celsius to 0 degrees Celsius during the day." "This deep temperature cycle wears things out." "So if we could drive quickly and do it in as few number of days as possible it would be the fewest number of thermal cycles as possible." "NARRATOR:" "It looks like easy driving most of the way, so they decide to put the pedal down and get to Victoria Crater as fast as they can." "maxwell:" "They basically handed us the keys and said, all right, you've got this big parking lot from here to there." "Go for it." "NARRATOR:" "Spirit, meanwhile, has survived its first winter on Mars, thanks to the solar power boost it got climbing the sunny north face of Husband Hill." "Along the way the rover finally sees something other than lava-- the first evidence of rocks that had been altered in some way by water or steam." "SQUYReS:" "Now, what we didn't see was lake deposits." "Remember that was what we went to Gusev for." "We went to Gusev for deposits that had been laid down long ago on a lake." "We did not find that." "But we were definitely starting to see a different side of Gusev Crater." "NARRATOR:" "The science is getting better, but the long climb has taken a toll." "Unlike Opportunity, whose solar panels have been blown clean by occasional gusts of wind," "Spirit has become so dirty it can barely generate enough power to survive the night." "But the rover's luck is about to change." "Its own cameras caught evidence that the windy season had arrived in Gusev Crater." "On sol 420, a random gust hits the rover, and suddenly it's clean again." "Spirit sent back this picture of its own deck just before the cleanup... and this one just after." "SQUYReS:" "It's a new lease on life." "We've got more power than we could use." "I mean, we have to shut the vehicle down during the afternoon to keep it from overheating, it's producing so much power." "It was, it was just astonishing." "NARRATOR:" "With power to spare, the summit called Husband Hill now seems within reach... if the rover drivers can find the route." "LeGeR:" "It seemed pretty audacious to think that we were going to actually be able to drive to the Columbia Hills and get there, much less get to the top of one of the peaks." "NARRATOR:" "There are good reasons to take a shot at this final, difficult climb, and they aren't all about science." "This is a chance for Spirit to achieve a goal no explorer has ever reached before-- the first ascent of a mountain on another planet." "maxwell: everybody who worked on Spirit wanted that accomplishment." "It wasn't so much about finding the liquid water anymore." "Now it was about climbing that hill." "NARRATOR:" "Meanwhile Opportunity is out on the open plains headed for Victoria Crater, sometimes making more than 200 yards in a sol." "CALLAS:" "It was just these gentle sloping dunes literally all the way to the horizon." "There wasn't a rock or a hazard to be seen anywhere." "And we figured, oh, gosh, you could drive blind in this area, it was so safe." "SQUYReS:" "We were using a driving technique that I think could be charitably described as bombing along at top speed with our eyes closed." "MAN:" "Flight, Mobility." "WOMAN:" "Go ahead, Mobility." "MAN:" "Up on screen number 3 is the trajectory the rover believes that it drove..." "NARRATOR:" "On sol 446, things suddenly come to a halt." "pictures from the previous sol pop up in mission control, and Opportunity's wheels are buried up to the hubs in deep sand." "maxwell:" "We got the images, and it was obvious from the very start that this was, as we say, off nominal." "Instead of being a hundred meters down the road, we we're buried up to our hubcaps." "NARRATOR:" "In the rover equivalent of rotating tires to extend their life," "Opportunity sometimes drove backwards during the long drive, and so had actually backed into its current predicament." "SQUYReS:" "The wheels broke through the surface, and we did 50 meters worth of wheel turns, thinking we were happily progressing across the Meridiani planum surface, and instead we were just digging slowly down and down into this, into the sand." "MAN:" "The wheels look like they're about 80 percent under the ground there." "NARRATOR:" "It's a potential disaster, and it takes some time to figure out what to do next." "SQUYReS:" "The first rule in a situation like that is don't do anything dumb." "MAN:" "It literally didn't make much more progress after about this point." "SQUYReS:" "We shouldn't have gotten into this mess in the first place, but let's not make it worse by guessing how to get out of it." "NARRATOR:" "They decide to simulate the situation on Mars, building a Meridiani sand dune, trying different materials to get the right consistency." "Then they bring in the test rover and spend two weeks experimenting with techniques to get unstuck." "FRANK HARTMANN:" "You have to very carefully think what do I want to do here?" "Am I going to keep spinning the wheels?" "Am I going to dig myself in deeper?" "Because no one really knows exactly what to do if you've got a rover on Mars that's, you know, buried up to its hubcaps in really, really fine dust." "NARRATOR:" "The best approach, as it turns out, is to put it in reverse and gun it." "But for a rover, gunning it happens in slow motion over two long weeks." "SQUYReS:" "We had to do 192 meters worth of wheel turns on Mars to get the vehicle to move one meter." "It took days and days and days." "You know, you'd do four meters, eight meters worth of turns and you'd come in the next morning and it went that far." "NARRATOR:" "On sol 484 Opportunity finally breaks free of the trap." "HARTMANN:" "After that, the driving mode changed dramatically, you know, because then we know what something looks like that can get us stuck." "And they were all the heck around us." "I mean, we were in a dune field." "NARRATOR:" "Opportunity's ordeal in the dune they call purgatory is a major speed bump on the road to Victoria Crater." "It will be a slow crawl the rest of the way through a dangerous maze of Martian dunes." "In September 2005, after more than a year of climbing," "Spirit reaches the summit of Husband Hill-- a short hike for a human, but a giant leap for a rover on Mars." "LeGeR:" "All the stuff that Spirit has done, all the places that it's been, all the things that it has seen, you or I could do in an afternoon." "But driving Spirit to the top of a 300-foot-tall hill on Mars is way better than any climb I've ever done." "maxwell:" "She stands there at the top of that hill that she's conquered now on another planet and she looks at the whole world around her." "I love her for bringing us that." "SQUYReS:" "More than anything else I think I felt, gosh, aren't we lucky to do what we do." "You know, we just climbed a mountain on Mars!" "Damn!" "maxwell:" "She's the best rover." "Opportunity's good, she's a good rover, but Spirit, man, that's a rover you've got to love." "NARRATOR:" "From the summit of Husband Hill," "Spirit spots the next target a mile away on the far side of the valley-- a formation of raised bedrock they call Home plate." "SQUYReS:" "It was a high priority thing for us largely because it just looked so different from everything else around it." "It was an obvious target to try to get to, but it was a long way off." "NARRATOR:" "There's no time to waste." "The seasons will soon be changing again, and they'll need another sunny hillside to survive the winter." "Five months later" "Spirit has examined the edge of Home plate and found that it's a volcanic deposit formed by an explosive eruption." "exactly how it happened is not clear." "But with winter closing in, they decide to move on to the sunny side of McCool Hill," "300 yards away." "Then things start going bad." "The right front wheel, which had been showing signs of wear, finally quits altogether." "SQUYReS:" "That came at a really bad time because we were trying to get onto the slopes of McCool Hill, and without that wheel functioning properly, we can't climb." "NARRATOR:" "At jpl, they experiment with 5-wheel driving techniques." "It's easier to drive backwards, dragging the wheel, but the rover can't climb, and the dead wheel tends to pull it off a straight course, which complicates the driving." "LeGeR: each day we only had an hour to an hour and a half of power, and we had to write these incredibly complicated sequences of, you know, sometimes 400 commands just to try to drive 5 meters." "maxwell:" "We were really in a race against the clock because we had something like three weeks before Spirit just wasn't going to have enough energy to survive the night." "And people were talking about her like she was the walking dead." "SQUYReS:" "We're learning to drive all over again." "The seasons are changing." "The power is getting less and less daily." "everybody's starting to get nervous, and then we get stuck." "CALLAS:" "We got into this, it was kind of like quicksand, and we couldn't get out of it." "So we were thinking, oh, my God, are we going to be stuck here and is the rover going to die here?" "maxwell:" "You know when you go to the grocery store and you get the shopping cart with the one stuck wheel and you're trying to get that down the aisle, driving Spirit at this point is a lot like trying to do that in quicksand... only your shopping cart is 300 million miles away" "and you have to drive it with a keyboard." "NARRATOR:" "It takes a week to get Spirit out of the trap, and now there's not enough time to reach the side of McCool Hill." "SQUYReS:" "Forget about the stuff hundreds of meters away." "We're never going to make it." "What do we got that's next to us?" "NARRATOR:" "With no time left on the clock, they settle for a spot nearby where they can straddle a low ledge and get a 1 2-degree tilt toward the sun." "SQUYReS:" "And that was it." "And there we sat for seven months." "NARRATOR:" "There's not much else to do now but wait for spring." "In September 2006, after 21 months on the flat plains of Meridiani," "Opportunity reaches the rim of Victoria Crater and the most spectacular vista yet seen on Mars." "The bowl is a half mile across, five times the size of endurance." "SQUYReS:" "The view, when we first pulled up to the rim, it was just like nothing we'd ever seen before." "It was like coming onto the Grand Canyon." "You know it's there, but it doesn't really prepare you for the enormity of what you're about to see." "NARRATOR:" "Millions of years of Martian history could be exposed in these rock faces, but to read it, they need to get close." "Opportunity sets off on a scouting mission that will last almost a year... a daring drive along the sheer edge of the crater wall, looking for access to the science down below." "SQUYReS:" "So we're literally tiptoeing a hundreds of millions of dollar vehicle along the top of a cliff on another planet." "If you can drive right out to the tip of one of those promontories, right to the edge, you can shoot across with your camera at the next promontory over, which might be only 30, 40, 50 meters away," "and you'll see this wonderful cliff exposed there." "But in order to get that view you've got to go right to the edge." "NARRATOR:" "After seven months, they've seen enough from the rim and are ready to go inside." "The best way in appears to be the spot where they first approached the crater." "So they send Opportunity back where it came from 200 sols before, unaware that a dangerous storm is on the way." "Near Home plate, Spirit has survived another winter and is moving again, dragging its dead wheel, digging a trench as it goes." "SQUYReS:" "We're driving along one day, in this little valley, and we look at the pictures of the trench that we dug that day, and there's this one spot where the soil was practically as bright as white snow." "That got our attention." "NARRATOR:" "They'd seen bright soil in the tracks before, but nothing like this." "SQUYReS:" "It turns out this stuff is more than 90 percent pure silica." "Not quartz." "This is not beach sand." "This is amorphous silica." "It's like opal." "All of the sudden we realize we've just come across something completely new and different that we had never seen before." "NARRATOR:" "This kind of silica almost certainly formed in an ancient hydrothermal system like hot springs or volcanic steam vents." "SQUYReS:" "And the thing that's cool about that is you can go to hydrothermal systems on earth and they're teeming with microbial life." "Now I don't know if there was microbial life here." "We didn't, you know, bring fossil detection instruments with us, but this is the kind of environment that could have been quite appropriate for some hardy types of microbes." "And that makes it a pretty important place." "NARRATOR:" "The presence of volcanic hot springs could explain the formation of Home plate itself-- an explosive mix of water and hot lava." "It's one of the most important breakthroughs of the mission, and chances are it would not have happened without the broken wheel." "maxwell:" "See, this is why Spirit's the best rover, because she takes her hardships and turns them into something positive!" "NARRATOR:" "By July 2007, Spirit and Opportunity have been on Mars three and a half years, defying all expectations of how long they would last." "But they're about to suffer a potentially fatal blow-- a massive summer dust storm on a scale that happens only once every three Martian years." "SQUYReS:" "Our first summer on Mars it didn't happen." "And our second summer on Mars it didn't happen." "But our third summer on Mars, it happened." "And it blew up into a global storm, blanketed the entire planet." "From where Opportunity sat on Meridiani planum, you looked up and you couldn't tell where the sun was in the sky." "The amount of direct sunlight that was reaching the solar panels was less than one percent of what it is on a clear day." "NARRATOR:" "At jpl they shut down all but the most essential systems on the rover to conserve power." "CALLAS:" "They were never designed to survive a dust storm." "The rovers are solar powered." "They need the sunlight to survive." "So each day we would turn things off, reducing the amount of power." "But, you know, you can't turn everything off because it's all about keeping the rover warm." "SQUYReS:" "One of the things that keeps the vehicle warm is running the computer inside." "And so there was this delicate balancing act between running the computer enough to keep it warm, but not running it so much that you draw the batteries down too much." "And we were just right on the edge of, of, of, uh, catastrophe." "NARRATOR:" "On the other side of Mars, the dust is not as heavy, and Spirit is weathering the storm with fewer problems... but there's a growing fear that Opportunity will not survive." "The engineers have done all they can, and now they just wait." "jake MATleVlC:" "It's like sitting at someone's deathbed, you know, and waiting and waiting and wondering is it going to survive, is it going to come back?" "is it going to be able to talk to us?" "And it was very agonizing." "It got to the point where you couldn't even take measurements to figure out how bad it was." "All you could do was just sort of sit there." "We just ran out of things to try." "NARRATOR:" "Soon the power will be so depleted that the rover will experience what's called a low power fault and simply shut itself down until it can recharge its batteries." "In the meantime, Opportunity could freeze to death." "maxwell:" "You kind of don't want them to go out like that." "You know, you don't want them to struggle and persevere and just sort of get killed by a blanket of dust." "It almost just doesn't feel right." "NARRATOR:" "When almost everyone has given up hope, the sky begins to clear, and the six-week ordeal finally comes to an end." "Still the lucky rover," "Opportunity comes through with clean solar panels thanks to a gust of wind and is ready to enter Victoria Crater." "And true to form, as the dust settles in Gusev Crater," "Spirit gets buried." "The five-wheeled rover is on top of Home plate, covered with dust and starved for power." "The seasons are changing once again, and Spirit needs another north-facing slope to survive yet another winter." "SQUYReS:" "The rover is so dirty from the dust storm that a 1 2-degree tilt is not going to cut it." "We need a 30-degree slope." "And this is a rover that can't climb 30-degree slopes." "NARRATOR:" "The only good option at this point is to drive across Home plate to the north rim where Spirit could back off the edge to get the tilt it needs." "ashley STROUpe:" "We had about 40 days to get there, and of course with the power situation already getting low we couldn't drive every day, and with that broken wheel we couldn't get far on every day of those drives." "So we really had to make the most of that time." "So we started driving across the top of Home plate to get to this parking spot." "And we drove right into a sand trap." "NARRATOR:" "They call it Tartarus-- the lowest level of hell-- a micro-crater full of sand too deep for Spirit to handle with five wheels." "STROUpe:" "It really began to look like we might not make it." "We weren't pointed anywhere near the sun." "We were absolute certain death in that configuration if we could not get out of there." "SQUYReS:" "We really got into a fix there." "The two back wheels were off the ground." "So they're not working at all." "The right front wheel is dead." "So a six-wheel vehicle now actually only has three wheels that are doing us any good whatsoever." "STROUpe:" "We had to get out, there was no choice." "We had to get out or the mission was over." "I had nightmares about just watching the rover slowly freeze to death in this crater." "NARRATOR:" "There's one last escape route to try, but it's right at the edge of Home plate." "The slightest mistake on the way out could send Spirit over the edge." "SQUYReS:" "We had tried every single trick we had." "And if that drive didn't work, the mission was probably over." "STROUpe:" "We sequenced it, and we sent it up to the rover." "And a lot of us got no sleep that night." "NARRATOR:" "With no margin for error," "Spirit creeps out of the pit and along the edge of Home plate." "SQUYReS:" "And it worked." "We got out of Tartarus, we got across Home plate, and we made it to the north side, eased our way down onto that 30-degree slope, and because of that, we have a fighting chance of actually making it through our third winter on Mars." "NARRATOR:" "It's been five and a half years now since the twin rovers landed on Mars." "In September 2008, Opportunity climbed out of Victoria Crater and set off on another journey it may never complete-- a seven-mile trek to a massive crater more than 20 times the size of Victoria." "It could take two years to get there." "Spirit survived the winter, but since then it's had a tougher time, with computer glitches and bouts of amnesia." "STROUpe:" "These rovers are pretty old now." "They're getting kind of arthritic." "They don't see quite as well anymore because the cameras are getting more and more coated with dust, so their vision's getting a little fuzzy." "NARRATOR:" "In May 2009, Spirit got stuck in another sand trap and hasn't moved since." "They're searching for solutions at jpl, hoping that Spirit can dodge yet another bullet." "SQUYReS:" "They're going to die when they die." "You know, at this point, every day is a gift." "We just push the vehicles as hard as we can, um, enjoy them while we've got them." "And someday they're going to die, and I don't know when." "NARRATOR:" "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." "SQUYReS:" "I used to have this na'i've idea that at some point we'd be able to sit back and fold our arms and say, yeah, well, we did it." "You know, we've learned everything we can about Mars at these places 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 anymore." "And you'd like to think at that point, well, you turn it off." "Well, we can't turn them off." "They don't have an off switch." "Um, 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 you can send that says, OK, you're done." "NARRATOR:" "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 even if no one is listening." "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." "SQUYReS:" "It's cold, it's dry, there's no vegetation." "They're not going to rust or anything like that like." "You know, these things could be still sitting there with their aluminum surfaces shining a million years from now." "They're going to last a long, long time." "Longer than most things that humans have ever built."