|Volume: 02, Issue: 01||01/14/2004|
Spirit Continues Explorations on Mars while Opportunity Races ForwardOne of NASA’s traveling robotic geologists, Spirit, has landed on Mars and returned stunning data and images of the area around its landing site, named Columbia Memorial Station, in Mars’ Gusev Crater. As Spirit made its landing, the second Mars Exploration Rover, Opportunity, hurtled on toward its Jan. 25 landing date.
Spirit successfully sent a radio signal after the spacecraft had bounced and rolled for several minutes following its initial impact at 11:35 p.m. EST on Jan. 3. Three hours later, the rover transmitted its first images to Earth, relaying them through NASA's Mars Odyssey orbiter.
"We're back,” said NASA Administrator Sean O'Keefe. “I am very, very proud of this team, and we're on Mars."
The images sent by the rover have excited scientists about the prospects of exploring the region after the egression, or roll-off, from its lander platform onto the Martian surface. The terrain looks different from any of the sites examined by NASA's three previous successful landers - the two Vikings in 1976 and Mars Pathfinder in 1987.
By correlating images taken by Spirit with earlier images from spacecraft orbiting Mars, the mission team has determined that the rover appears to be in a region marked with numerous swaths where dust devils have removed brighter dust and left darker gravel behind.
"This is our new neighborhood," said Dr. Steve Squyres of Cornell University in Ithaca, N.Y., principal investigator for the science payload. "We hit the sweet spot. We wanted someplace where the wind had cleared off the rocks for us. We've landed in a place that's so thick with dust devil tracks that a lot of the dust has been blown away.
"What we're seeing is a section of surface that is remarkably devoid of big boulders, at least in our immediate vicinity, and that's good news because big boulders are something we would have trouble driving over," Squyres said. "We see a rock population that is different from anything we've seen elsewhere on Mars, and it comes out very much in our favor."
Geologist Dr. Matt Golombek of NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., co-chair of the steering committee that evaluated potential landing sites for Spirit and Opportunity, said pictures are confirming some predictions about the Gusev site. Rocks cover less of the ground than at the three previous Mars landing sites -- about three percent of ground area around Spirit compared with about 20 percent of the ground around each of Mars Pathfinder, Viking 1 and Viking 2.
Presenting the latest high-resolution color mosaic from Spirit, Golombek said, "This is without question the smoothest, flattest place we've ever landed on Mars, with the possible exception of Viking 2."
The first stereo image mosaic from Spirit's panoramic camera provided more details of the landscape's shapes, including hills about 2 kilometers (1.2 miles) away that scientists are discussing as a possible drive target for the rover after its egression. Scientists were also delighted to discover "Sleepy Hollow," a shallow depression in the Mars ground near the rover that may become another target destination.
Another of Spirit’s image products shows a patch of intriguing soil near the lander in greater detail than an earlier view of the same area. Scientists have dubbed the patch "Magic Carpet" for how some soil behaved when scraped by a retracting airbag.
"It has been detached and folded like a piece of carpet sliding across the floor," said science-team member Dr. John Grotzinger of Massachusetts Institute of Technology, Cambridge.
Additionally, traces of carbonate minerals showed up in the rover's first survey of the site with its infrared sensing instrument, called the miniature thermal emission spectrometer, or Mini-TES. Carbonates form in the presence of water, but it's too early to tell whether the amounts detected come from interaction with water vapor in Mars' atmosphere or are evidence of a watery local environment in the past, scientists emphasized.
"The beauty is we know how to find out," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the mission. "Is the carbonate concentrated in fluffy dust? That might favor the atmospheric hypothesis. Is it concentrated in coarser material? That might favor the water hypothesis."
These questions and others may be answered when Spirit leaves the landing pad that has been its home since arriving on Mars.
"We're about to kick the baby bird out of its nest," said JPL's Kevin Burke, lead mechanical engineer for the rover's egress off the lander.
Spirit's next step in preparing to drive onto the surface of Mars is to sever its final connection with the lander platform by firing a cable cutter, which Burke described as "an explosive guillotine." The planned sequence after that is a turn in place of 115 degrees clockwise, completed in three steps on Jan. 13 and 14. If no obstacles are seen from images taken partway through that turn, drive-off is planned toward the northwestern compass point of 286 degrees.
Over a 24-hour period from Jan. 10 and 11 -- the rover's 8th Martian day on the planet, or "sol 8" -- pyro devices were fired slicing cables to free the rover's middle wheels and releasing pins that held in place its instrumented arm. The arm was then locked onto a hook where it will be stowed when the rover is driving. Spirit also successfully completed its stand-up activities by extending the rear wheels, putting the rover into a fully opened configuration for the first time since pre-launch testing in Florida last spring.
"Spirit has spent most of the last seven months scrunched up inside of a tetrahedral-shaped lander, and that is not the shape a rover wants to be,” said JPL's Chris Voorhees, who led the engineering team that planned the unfolding sequences for Spirit and Opportunity. “Over the last several days, Spirit has performed a sort of reverse robotic origami."
"The rover now stands at its full height, and all six wheels are in position for driving on the surface of Mars," said Jennifer Trosper, mission manager at JPL.
Although Spirit remains attached to its lander for the moment, the rover has returned valuable data and images to scientists. Some of the most important findings are the images taken by its panoramic camera, which recently completed a 360-degree view of Spirit’s surroundings.
"The whole panorama is there before us," said rover science- team member Dr. Michael Malin of Malin Space Science Systems, San Diego. "It's a great opening to the next stage of our mission."
The color panorama is a mosaic stitched from 225 frames taken by Spirit's panoramic camera. It spans 75 frames across, three frames tall, with color information from shots through three different filters. The images were calibrated at Cornell University, Ithaca, N.Y., home institution for Dr. Jim Bell, panoramic camera team leader.
Malin said, "Seeing the panorama totally assembled instead of in individual pieces gives a much greater appreciation for the position of things and helps in developing a sense of direction. I find it easier to visualize where I am on Mars when I can look at different directions in one view. For a field geologist, it's exactly the kind of thing you want to look at to understand where you are."
Pictures from Spirit's panoramic camera continue to provide details about the Martian ground and sky. The rover transmitted home about 180 megabits of science data in the past Martian day, nearly 10 times the maximum daily capability of Mars Pathfinder in 1997.
Spirit’s other instruments are also operating smoothly. According to Arthur Amador, one of JPL’s mission managers, the rover's status overall is "pretty darn perfect."
Amador described the communication link from Mars to Earth as excellent, allowing the team to receive 170 megabits of data during a 24-hour stretch. All science data stored on the rover has been sent to Earth. The rover is generating 900 watt-hours of power per day and using 750 watt-hours, and its thermal condition is good, he added.
The rover's infrared sensing instrument, called the miniature thermal emission spectrometer, has begun returning data about the surroundings, too, indicating that it is in good health. Positive health reports are now in for all of Spirit's science instruments.
In addition, plans call for the rover's miniature thermal emission spectrometer to "stare" at three selected sites to collect very low-noise data. Another science instrument, the alpha particle X-ray spectrometer, will be calibrated as well.
The flight team is also finding ways to prevent overheating of electronics inside Spirit. "Our robot geologist was dressed a little warm for the weather on Mars," Trosper said. The atmosphere and surface at the landing site this week are not as cold as anticipated. The rover's temperatures are expected to drop, however, when it rolls off its lander platform and gets its wheels onto the ground.
NASA chose Spirit's landing site, Columbia Memorial Station within Gusev Crater, based on evidence from Mars orbiters that this crater may have held a lake long ago. A long, deep valley, apparently carved by ancient flows of water, leads into Gusev. The crater itself is basin the size of Connecticut created by an asteroid or comet impact early in Mars' history. Spirit's task is to spend the next three months exploring for clues in rocks and soil about whether the past environment at this part of Mars was ever watery and suitable to sustain life.
Spirit traveled 487 million kilometers (302.6 million) miles to reach Mars after its launch from Cape Canaveral Air Force Station, Fla., on June 10, 2003. Its twin, Opportunity, was launched July 7, 2003, and is on course for a landing on the opposite side of Mars on Jan. 25 (Universal Time and EST; 9:05 p.m. on Jan. 24, PST).
"To achieve this mission, we have assembled the best team of young women and men this country can put together,” said JPL Director Dr. Charles Elachi. “Essential work was done by other NASA centers and by our industrial and academic partners."
President George W. Bush called on Jan. 6 to congratulate the rover flight team for reconfirming the American spirit of exploration, Elachi said.
JPL, a division of the California Institute of Technology, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington. Additional information about the project is available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.
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