A.J.S. RaylJan 28, 2004

Mars Exploration Rovers Update: Spirit Continues Progress in 'Rehab;' Opportunity Returns "Phenomenal" Images Challenger Crew Remembered

While the first Mars Exploration Rover, Spirit, continues to make progress in 'rehab,' members of the science teams are marveling at the images Opportunity is sending home.

The latest pictures from Opportunity reveal in better detail the striped and cracked layers of rock in the outcropping of bedrock just 26 feet (about 8 meters) away from where the second MER rover came to a stop last Saturday night.

The outcrop at first glimpse appeared to be rather large and imposing, something that initially concerned some engineers who wondered about Opportunity's ability to navigate up and over or around them. But as the pictures continued to stream in, especially the first images taken by the PanCam, the scientists had a chance to more closely examine the rover's immediate surroundings. They found "pretty phenomenal" detail, noted Jim Bell, lead scientist for the PanCams the images were projected at the daily news briefing. And, with that detail they discovered that the outcrop was composed of "tiny rocks," as lead scientist Steve Squyres described them.

"The thinnest layers we're seeing are a centimeter -- the thickness of your finger -- so they are very small features," Squyres said. "The highest point is a foot. That means this will be significantly less threatening to the rover, significantly easier to access, because you can drive right up on it."

Once the science teams get the chance to check out this formation up close with Opportunity's payload of instruments, they will in all likelihood be able to reconstruct the geologic events that formed the various layers, according to both Squyres and science team member Andrew Knoll, of Harvard University.

While the science teams, obviously, have no way of knowing yet what the composition of the rocks in the outcrop is, they do have two primary working hypotheses. One holds that this bedrock was formed by falling volcanic ash; the other proffers they were formed by sediments deposits carried there by water or wind, or both. "We should -- with Opportunity's unique payload -- be able to distinguish between those two hypotheses," offered Knoll.

This outcropping of bedrock "blew away" the science team -- as Squyres put it -- not only because it is the first bedrock ever found on Mars, but because it could possibly, quickly reveal whether water played a role in its formation, and perhaps reveal whether Meridiani Planum ever boasted an environment capable of sustaining life as we know it. If they do turn out to be sediments, water will have been almost certainly involved, Squyres noted. "I doubt these are windblown deposits," he said. Water would be appear in this case to be more likely, Knoll agreed, than wind.

Still, a "key Issue" is the duration or persistence of the water. "We have known for sure from orbital images that there has to be role for water . . . [that's] a big question that we hope Meridiani will address -- is it alright to have water for short bursts or do we need persistent water for thousands, millions of years?" expounds Squyres. "In that regard, both Gusev and Meridiani are interesting places to go, because the entering hypotheses were -- what we see at Gusev and the iron at Meridiani -- could be consistent with persistent water.."

"This lighter unit [of rock] is very widespread and covers thousands of square miles just beneath the surface [of this fine-grained, dark red gray soil] at Meridiani," Knoll added. "Any kind of mechanism we think about has to be one that is not only reasonable in terms of what we can see at the level of this crater we've plunked into, but has to apply to a much larger area," he pointed out.

"We think these are very old features simply based on the distribution of large craters in the area -- although the terms old and young on Mars come with lots of uncertainty -- but certainly the features we're talking about [are] billions, maybe multiple billions of years of age," added Knoll.

The images alone, of course, as amazingly crisp and clear as they are, will not be able to reveal how the outcrop was formed. "We're probably going to get tantalizing hints from a distance, but the beauty of it is that we can go there," Squyres enthused. "And when we get close, we're going to do a very good job of characterizing what's there. It's going to be fascinating beyond words to get up close and personal with this thing. We're about to embark on what could be the coolest geological field trip in history."

The science teams also hope to determine the relationship between those light-colored rocks layers and the dark soil that covers most of the surrounding terrain. The hematite that was first identified from orbital studies, and which lured them to Meridiani in the first place, may be present in the dark soil, many of the scientists theorize now.

Other new show detailed impressions left in the dark, fine-grained soil left by Opportunity's airbags as the spacecraft was rolling to a stop in the small crater where it now sits. "These marks are telling us about the physical properties of the material," noted Jim Bell, lead scientists for the PanCam.

Some scientists believe that these dark granules, which cover most of the crater's surface, were pressed down into an underlying layer of powdery, lighter red material when the airbags hit. Others contend that the dark granules are agglomerations that crumble into the finer, lighter material when disturbed. After roll-off, that soil near the lander will be Opportunity's first target for close-up examination with her microscopic imager and the Mössbauer Spectrometer and the mini-thermal emission spectrometer, two instruments that can measure the composition. The soil at Opportunity's landing site appears to have different properties than the soil at Spirit's landing site, Bell pointed out.

In addition to returning images, Opportunity is going through the process of unfolding itself and getting ready to stand up and prepare for egress. So far, she has untucked her front wheels and latched her suspension system in place, critical steps in the preparation to drive off the lander and onto this Martian pay dirt. "The mechanisms really performed flawlessly," offered MER team member Rick Welch, activity lead for preparing the rover for roll-off, said earlier today.

Overnight tonight, the team plans to try tilting the lander platform down in the front by pressing the rear petal downward to raise the back. "What we want to do is lower the front edge by about 5 degrees," explained Welch. if all goes well, Opportunity will pull straight forward and drive straight off, as early as overnight Sunday-Monday.

Mission Manager Jim Erickson was pleasantly adamant in saying "We are going to go through the steps and get the rover off when it's ready to get off. We're taking a lot of care with what Jennifer [Trosper] is finding on Spirit to make sure we're not going to duplicate those issues . . . [and] have same problem as Spirit."

While Opportunity has successfully deployed and tested her high-gain antenna she is losing some of her battery charge each night, because of what appears to be a drain by an electric heater at the shoulder joint of her robotic arm, Erickson informed. A thermostat turns on the heater whenever the air temperature falls to levels that the rover is experiencing every night. The heater is not really needed when the arm is not in use, but ground control has not been able to activate a switch designed to override the thermostat, he explained. Engineers are working now to confirm the diagnosis, determine the ramifications of the power drain, and propose workarounds or fixes.

As for Spirit, Mission Manager Jennifer Trosper said: "We are working to get complete control of the vehicle, and we still aren't there yet."

Engineers working on Spirit's Anomaly Team have completed their analysis -- of initiating the same problem in a testbed simulator of the rover's electronics -- and the results supported the primary diagnosis of a glitch in management of the flash memory, reported Trosper. As a result, the team is continuing to carefully select data files to delete from Spirit's flash memory and is still considering sending up new software to help restore her to good health.

They are trying, however, to save as many of the science files that did not get sent down when Spirit suddenly stopped and 'froze' in place last Wednesday, January 21. Included in those data files is the science collected on the first-ever collaborative study of the Martian atmosphere, completed when the European Space Agency's Mars Express, using its set of instruments to take measurements while looking down toward Spirit from its vantage point about 186 miles (300 kilometers) above the landing site, as the rover looked up with its Mini-Thermal Emission Spectrometer, Mini-TES. The information collected from that collaboration would present a more accurate 'picture' of the Martian atmosphere at that place and time.

The files held for now in her flash memory also include early data collected by Spirit's Mössbauer Spectrometer and its Alpha Particle X-ray Spectrometer of the rock, Adirondack, that the rover was studying when things went awry. Even in a worse-case scenario, all the data Spirit's flash memory now holds could be, collected again. "The rover hasn't gone anywhere," Squyres said. And, Mars Express will pass again over the site.

Spirit's A-Team has also determined that the high-gain antenna on the rover is most likely in working order, despite earlier hints of a possible problem. That is especially good news since that antenna is used for direct-to-Earth communications.

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