Mars Exploration Rovers Update: Opportunity Finds Martian 'Paydirt,' Rolls Onto Surface Spirit Makes A Comeback
Posted by A.J.S. Rayl
31-01-2004 11:00 CST
Both Mars Exploration Rovers -- Spirit and Opportunity -- are down in the Martian dirt and getting to work.
The second rover -- Opportunity -- rolled off her lander and onto the dark red, Martian soil at Meridiani Planum early Saturday morning, at about 1:50 a.m., Pacific Standard Time (PST), just one week after arriving at the Red Planet.
During the last 48 hours, Spirit, meanwhile, has made an impressive comeback, returning new data and images after a week of silence caused by her computer 'crashing,' an event that stopped her cold, like a 'tin woman' frozen from movement in this land of 'ahhhs.'
Opportunity wasn't scheduled to roll off her lander until Saturday night/Sunday morning. But as fate would have it opportunity knocked -- and ground controllers and scientists decided early yesterday to move up the time for roll-off by nearly 24 hours, to the rover's seventh Martian day since landing.
"We're ahead of schedule and taking advantage of the fact that Opportunity treats us well," said Daniel Limonadi, rover systems engineer said.
Although conducting a bit less science before leaving her lander platform than Spirit did, the beta twin wasted no time in achieving a few 'firsts' of her own for the record books. As the robot geologist prepared for egress, from her position near the center of a small crater 72 feet (22 meters) across and 10 feet (3 meters) deep, she returned enough stereo images to map the crater. This was the first time a crater on another planet has been mapped from inside the crater.
The same stereo images have enabled scientists to create a new three-dimensional model of the crater that is providing a reference for rover driving within the crater, and later for choosing a route out onto the surrounding plains, science team member Ron Li, of Ohio State University, Columbus announced yesterday.
That data, along with the 'mission success, 3-D color panorama, as well as some other images and data was enough to satisfy the scientists and so the team voted 'all systems go' for Opportunity to roll off early this morning.
When Opportunity returned the first signal indicating she had begun her journey, the members of the MER team in the mission control center at the Jet Propulsion Laboratory (JPL) cheered and gave the thumbs-up sign, as the strains of The Who's "Going Mobile" rocked the room.
Confirmation that Opportunity had safely navigated the 10-foot (3 meter) drive straight down the lander ramp and onto the surface arrived about an hour and 10 minutes later, from data relayed by Mars Odyssey at 3:01 a.m. PST.
"And it looks like the astrobot made it," Flight Director Chris Lewicki noted, referring to Sandy Moondust, one of the Planetary Society's Martian 'explorers.' Moondust and her comrade, Biff Starling, are the tiny LEGO® minifigure characters who 'hitched' their rides to the Red Planet on the DVDs carried by Spirit and Opportunity. [Moondust had not been so lucky in the testbed, where she experienced an accident and was flattened (even more) by the rover.]
Opportunity's first post-roll off postcard -- taken by her rear hazard camera shows the now empty lander and the set her tire tracks leading away from it, much like the image returned by Spirit when she rolled off her lander a little more than two weeks ago.
"We knew it was going to be a good day," began Mission Manager Matt Wallace at the 3:45 a.m. news briefing. "Opportunity woke up this morning to 'Born To Run' by Bruce Springsteen. It turned out to be good choice. Up to the time she was born, which was only about two years ago, this vehicle has been a blue collar, hard-working machine, and she's got the scars to prove it. But like the team that designed and built her, she would not quit and she is now where she's supposed to be on Meridiani."
The cork was popped and the team members on the dais shared in what has become a traditional champagne success toast, as other team members clapped and cheered from the backs of JPL's Von Karman Auditorium. "Nothing went wrong," reported Kevin Burke "It was pretty smooth. After years and years of practice, we couldn't have dreamed it could have been this simple," said the lead mechanical engineer for impact-to-egress, who was given the honor of initiating Opportunity's roll-off.
"In my wildest dreams, I never thought they'd let a mechanical engineer touch a computer in Mission Control," Burke chuckled, as he recalled his 'magic moment' earlier this morning. "But there was precedence. When we did the bump, just before the egress, [JPL engineer] Chris Vorhees had the honor of pushing the button, so somehow the mold broken -- and then I got to hit the button. We've done it hundreds of times in test beds, and on the flight-like vehicles, but it's a little different to hit that button and send that command millions of miles away now that it's true commitment. It was pretty darn neat."
"It's one small click for --" broke in Wallace, causing the packed room to break out once again in laughter.
The engineers did have to make, however, a few slight adjustments. "We landed on a side petal and the way airbags [are pulled] underneath the lander made the landing platform a little less stable, so one of the things we did was to hyper-extend the rear petal to get us a little lower deck height from off front," Burke explained. "It also [made] up a little pitchy." That caused the lander to tip forward with the rover as Opportunity rolled down the ramp and into the Martian dirt; consequently, she "yawed about 7 degrees off the straight path," Burke noted. But the robot field geologist ended up just about one meter away from the lander, "exactly what we were shooting for."
"Mars threw us a few less curve balls than last time; on the other hand, I think we're getting pretty good at this," offered Joel Krajewski chief engineer for impact-to-egress. His colleagues on the dais and in the audience immediately began 'shushing' him. He smiled and responded: 'We'll talk about that next year.'"
There are three reasons that Opportunity rolled off on her seventh Martian day, said Krajewski, as opposed to Spirit, whose egress wasn't commanded until her 12th day. "The first reason is that we had very few surprises to deal with . . . a stuck [heater] switch . . .but other than that, everything else was nominal, so we had less things to juggle. The second reason is that we are getting practiced at it . . . just like all of us get better at driving [a car], we all get better at driving [these rovers]. The third reason is that we've learned how to do things in parallel more than we had before . . . and the flexibility of moving things back and forth helped a great deal -- and is a credit to our P.I . [Steve Squyres] who had the foresight and the trust -- and [shared] the sheer terror of the situation," he added.
"But it did all fall into place, remarkably," Krajewski continued. "Just about every subsystem is as good or better than we ever saw it in here. We're ready to roll onto the real mission."
Today, Opportunity's ground team will instruct the rover to test her arm and inspect her instruments, in preparation for her first experiments, added Chris Salvo, flight director for impact-to-egress.
Hematite: Martian paydirt
Opportunity shares the same mission with Spirit -- to explore her area's geological history and search for signs of water, past and present. The rover would appear to have been as anxious as the scientists for she managed, even before touching one wheel to the Martian surface, to confirm the presence of hematite, the iron oxide that on Earth usually forms in processes involving water. An enormous amount of hematite had been measured at Meridiani Planum from Mars Global Surveyor's thermal emission spectrometer (TES), a couple of years ago, and the gray crystalline mineral is the main reason the site was chosen for exploration.
In the wee hours of this morning, Phil Christensen, lead scientist for the Mini-TES instrument, from Arizona State University, broke the news officially: "The Mini-TES has indeed discovered hematite on surface of Mars," he said, and more cheers and whistles erupted from the crowd in the auditorium.
"I personally am not surprised we found it at Meridiani, but based on the reaction of some of my colleagues, they seem more surprised that I was right the first time around," added the always mellow Christensen.
More champagne, more cheers. "I can do that," Christensen said holding out his plastic glass. "It's third time I've been drinking today," he smiled. Indeed, Opportunity had hit the target mineral -- Martian paydirt -- and he had a lot to celebrate.
Although the New York Times' Kenneth Chang had broken news of the hematite confirmation in yesterday's edition of the newspaper, the scientists in the news briefing yesterday had not been willing to confirm it. All Deputy Principal Investigator Ray Arvidson would say is: "If you look at any of the Mini-TES [team] members, they have huge smiles on their faces."
It didn't take a rocket scientist to figure out the underlying meaning of that answer. But this was Christensen's moment, and early this morning, he basked in that moment and expounded on the details.
"The strongest signature we see of hematite is from the dark, granular loose material on top of [the] bedrock," he reported. "So it's very likely that the source of the hematite is a rock layer that sits on top that bedrock. And over course of the next weeks, we're going to go chasing that rock layer and really try to find what its origin is."
What they found, he pointed out, is "not pure hematite," Christensen pointed out. "There [are] other materials, and we're working hard to find out what those are."
The spectrum the Mini-TES team acquired of hematite is "distinctive" of two origins -- a low temperature origin and a high temperature origin, Christensen explained, adding that there are two mechanisms, the team is most seriously considering.
"One way to form this material is precipitation from water at low temperatures," he explained. "It can form a variety of amorphous iron materials -- iron ooze, and that can convert to a set of minerals, one being called goethite and that over time converts to hematite. That is consistent with spectral signature we see. From the data we have so far, the spectrum matches best for a low temperature origin for the hematite.
"Another scenario is you take magnetite, which is a common volcanic material, and convert it to hematite at very high temperature and that has a slightly different spectral signature," Christensen continued.
While the Mini-TES spectrum from Mars best matches the spectrum converted from goethite, "rather than other way around," Christensen stressed that the low-temperature origin theory does not eliminate the possibility that this Martian hematite was formed via volcanic processes. "The key is [looking] at the full context, " he added. "You could have volcanic ash deposition and weather that iron material again and again, down to an iron oxide. There are still plenty of opportunities -- ground water opportunities, hydrothermal opportunities If you think about it, we measured a very similar spectrum [of hematite] from orbit -- and what we've done [now] is confirm it's there. And, we have a better idea of where it is. But all of the possibilities are still very much open."
More and better data, in all probability, will reveal the answers as to where and how and when this hematite formed on Mars. The Mössbauer, along with Opportunity's other instruments should reveal, Christensen noted, "any traces" of a low temperature precursor. "The Mini-TES can detect from a distance minerals to a few percent level and the Mössbauer can do better than that, so if there are still tracers of precursor mineral, then that will help nail down what it's origin is," he explained.
The team is particularly eager to use the Mössbauer spectrometer, which is specifically designed to detect and measure minerals that contain iron to a high degree of accuracy With the Mössbauer data, the scientists should be able to determine the composition and abundance of the hematite, as well as other minerals present. "I hope that a clue might come from the Mössbauer," Christensen said. "If the conversion is not 100 percent, there may still be remnants of that goethite or iron oozes or of magnetite around, that plus [the images from] the microscopic imager (MI) where [we can see] where is this hematite - is it in coatings on grains or in other grains -- those other pieces of information will be necessary to figure that out."
Remarkably -- and quite unexpectedly -- even before Opportunity opened her petals or began preparations for egress, she "performed [her] first experiment," Christensen pointed out. As the lander package was retracting the airbags that cushioned the rover's bouncing arrival, it made drag marks in the soil, disrupting the soil and changing the appearance of its color where the marks cut into the ground. "The air bags actually altered the surface enough so that it appears the hematite is carried in the coarse material and in the fine red material underneath it, we don't see this hematite signature," he explained. "We looked at spectrum and amazingly just next to the bounce marks, we see beautiful signature and in bounce marks itself we not see hematite."
In addition to TES-ing the layering on top of the bedrock, the team also pointed the instrument at the bedrock. "One of our goals is to see what it's made of, but all I can say at the moment is what it's not," Christensen said. "Some of the [hypotheses of] origins for hematite argue for quartz. We don't see that in the bedrock. The bedrock does not appear to be carbonates, and that white unit does not have hematite. So the white marker bed is going to be extremely exciting to explore over the next few weeks."
The second rover's prime directive now is to take microscopic images and spectrometer readings of the dark gray-brown-red soil close to the lander. Once that task is completed, the robot field geologist will head out to the outcrop of bedrock about 26 feet (8 meters) northwest of the lander - what will be about a two-day drive. The scientists estimate they'll probably start that drive sometime mid-week next week.
The team still does not know exactly where Opportunity is in Meridiani Planum, but, they assured, they will know soon.
The evening did not pass without a fair share of Academy Award like speeches of 'thank-yous,' but one group was especially remembered, in addition to the contractors and vendors, and the families, by Mission Manager Wallace. "I want to acknowledge a more mature group of engineers -- the men and women sprinkled through our management here at the lab and [who] we pulled out of retirement to work with us on our technical boards. They really gave us the insight and steady hand we needed to get through these last three years. They are the men and women who built these great programs -- the names of which you know -- Voyager 1 and Voyager 2, Viking 1 and Viking 2, Galileo, Cassini, and Mars Pathfinder from which we stole so much ingenuity and talent. I just want to say thank you to those people," he said. "They are out there and a big part of this. If we are explorers, they are the pioneers."
The comeback kid
On the other side of Mars, Spirit shined in her own way yesterday as the 'comeback kid' on her way to making a full recovery.
Yesterday, the MER team presented the first images the rover has taken with the panoramic camera and returned since she 'conked out' on the 18th Martian day of her mission. The images were acquired two days ago, on Sol 26, and among other things they demonstrated that the camera's health had remained excellent during the rover's time in 'rehab.' Among those images are views of two light-colored rocks that have been named Cake and Blanco, both of which are possible targets for up-close examination.
First, however, the plan calls for Spirit to finish what she started on Adirondack, over the next few days, including using her rock abrasion tool to 'RAT' the rock, or in other words, grind into it to see what's inside. She returned microscopic images and Mössbauer spectrometer readings of Adirondack taken the day before she developed computer and communication problems and stopped working. Both are unprecedented investigations of a rock on another planet.
Incredibly, the microscopic images indicate Adirondack is a hard, crystalline rock. "If you had a hammer and whacked that rock, it would ring," Arvidson said yesterday.
Later plans now call for Spirit to examine a nearby whitish-colored rock, then drive toward a crater named Bonneville, which is about 820 feet (about 250 meters) away. The scientists will use the rover to search for rocks that may have been excavated from below the surface and tossed outward by the impact --known as 'ejecta' -- that dug the crater.In the meantime, engineers are continuing to restore Spirit to health as the rover makes scientific observations, said Mark Adler, mission manager. They plan to delete from the rover's flash memory a large amount of information stored before landing, then resume operating Spirit in a normal mode that uses flash memory. The team anticipates that Spirit will make a complete recovery.