The first of NASA's two Mars rovers landed safely on an open stretch within Gusev Crater on Saturday night and sent back dozens of black-and-white images, marking a successful start to NASA's first ground-level exploration of the Red Planet in more than six years.
Controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., whooped, clapped and hugged each other shortly before 9 p.m. PT (midnight ET) when they heard that a carrier tone was received from the Spirit rover. That signal, relayed by NASA's orbiting Mars Global Surveyor, confirmed that the spacecraft had landed intact and right side up.
The applause was renewed hours later when Spirit rover linked up with another NASA orbiter, Mars Odyssey, and sent its first batch of snapshots. The first image showed the spacecraft's sundial/calibration target, and soon the screens at JPL were filled with panoramas of level Martian terrain, littered with rocks. In all, NASA received 60 low-resolution images from the rover, plus three more from the spacecraft's descent camera.
Coming on top of a successful comet flyby on Friday, the Mars landing provided a welcome boost to an agency that was still coping with last February's loss of the space shuttle Columbia and its crew. At a post-landing news conference, NASA Administrator Sean O'Keefe poured champagne and toasted the mission team.
"This is a very big night for NASA — we're back!" he told reporters. "I am very, very proud of this team, and we're on Mars."
From hell to heaven
Plenty could have gone wrong during the final stage of the rover's seven-month, 300-million-mile (480-million-kilometer) trip to the Red Planet — a descent through the atmosphere that NASA's associate administrator for space science, Ed Weiler, had called "six minutes from hell."
"It was six minutes from hell," Weiler said Saturday, "but in this case we said the right prayers that got us up to heaven."
On the way down, the spacecraft's heat shield weathered more than 2,600 degrees Fahrenheit (1,450 degrees Celsius) during the plunge through Mars' thin atmosphere.
That friction slowed down Spirit, wrapped in its landing shell, from a speed of 12,000 mph to 1,000 mph (19,200 to 1,600 kilometers per hour). Retro rockets and a parachute slowed the descent even more.
About 50 feet (15 meters) above the Martian surface, airbags inflated around the rover and its shell to cushion the impact.
Protected by the airbags, the spacecraft could have bounced as high as a four-story building, rolling to a stop as much as a half-mile (1 kilometer) from the initial impact. Even if everything up to that point worked perfectly, strong cross winds and a particularly sharp rock could have blown a gaping hole in the plan.
Spirit had been programmed to transmit radio tones for relay via Mars Global Surveyor or another NASA orbiter called Mars Odyssey. Controllers heard the confirmation of a safe landing within 15 minutes after impact.
Weiler told reporters that the relay system was a milestone in space exploration. "For the first time in history, we have an interplanetary communication network," he said.
During the hours that followed, the spacecraft's airbags were deflated and the landing shell's petals opened to reveal the 384-pound (175-kilogram) rover within.
The first crop of images marked an exceptionally fast start to Spirit's 90-day mission to look for traces of ancient water in Gusev Crater. Such a quest is considered key to resolving the question of whether Mars could have sustained life billions of years ago.
Looking for water and lifeToday, Mars is a cold and dry place, inhospitable to life as we know it — at least on the surface. But based on the evidence collected by past Mars missions, scientists believe that the Red Planet was once warmer and wetter, with liquid water flowing through channels and pooling in lakes or even oceans. On Earth, life is found virtually everywhere liquid water exists.
On Mars, Gusev Crater is thought to have been an ancient lakebed, and Spirit will analyze the rocks and soil to determine whether liquid water could have persisted there long enough to support the development of life.
"We don't know that there's life there, or that there ever was," Cornell University astronomer Steve Squyres, principal investigator for the rovers' scientific payloads, told MSNBC.com in advance of the landing. "I would be willing to bet a year's pay that water flowed there on the surface sometime in the past. But that's as far as I'd be willing to go."
Early Sunday, Squyres told reporters that Spirit had ended up in a scientific "sweet spot." He noted that although there was a good variety of rocks for analysis, the terrain was still clear enough that "we're going to be able to really motor around this place."
Later in the day, Squyres said the rover imagery matched up with a picture from Mars Odyssey, providing a tentative location for Spirit and revealing an area marked by dust devil tracks.
"We've landed right in a place so thick with dust devil tracks that a lot of the dust has been blown away," he said.
Squyres also pointed out depressions that offered interesting targets. "They could be impact craters, they could be what geologists have called deflation hollows," he said. On Earth, deflation hollows typically collect water runoff.
Still unclear was whether a large dark object at one corner of the lander was a rock, as initially suspected. If so, it could block the landing ramp and force the rover to turn around and roll down another ramp. On Sunday, NASA said the object could also be a dust-coated piece of one of Spirit's large air bags.
“If anything didn’t go quite right, that may be it,” said Jennifer Trosper, Spirit’s mission manager for surface operations.
The rover will start by collecting images and other scientific data from where it sits. Even if the spacecraft has landed in perfect condition, it will be at least nine days before the rover rolls off its landing platform to begin its travels.
Spirit's twin, the Opportunity rover, is due to touch down on Mars just after 9 p.m. PT (midnight ET) Jan. 24, rounding out the $820 million mission. Opportunity is targeting a geologically complex region called Meridiani Planum, which contains significant deposits of hematite, a mineral that could have been formed through the action of ancient hot springs. On Earth, such springs provide a home for microbial life.
Lessons learned
Previously, two in every three attempts to land spacecraft on Mars has failed. The latest apparent failure was the British Beagle 2 lander, which has not been heard from since its Christmas descent to the Martian surface. Japan's Nozomi orbiter also missed going into Martian orbit last month.
Before Spirit, only three Mars landers were able to carry out their missions successfully: the two Viking spacecraft that landed in 1976, and the Mars Pathfinder lander/rover, which wowed millions of onlookers worldwide in 1997.
In December 1999, NASA’s Mars Polar Lander crashed in the planet's south polar region because of a software glitch. That setback came only three months after NASA's Mars Climate Orbiter was lost, basically due to a mixup between measurements in feet and meters. The twin failures of 1999 forced the space agency to overhaul its entire Mars exploration program, adding money and manpower to ensure that everything was done right this time around.
Opportunities to send spacecraft to Mars efficiently come around only every 26 months: The space agency decided to send two identical rovers this year to provide an extra measure of redundancy and take advantage of the closest encounter between Mars and Earth in almost 60,000 years.
Mars Global Surveyor and Mars Odyssey were sent to the Red Planet in 1997 and 2001, respectively, and are still carrying out mapping missions that have surpassed expectations. Now they will serve as relay satellites for rover data as well.
The European Space Agency's Mars Express spacecraft, which carried Beagle most of the way to Mars, joined Global Surveyor and Odyssey in orbit on Christmas and is being positioned to search for the missing Beagle.