PASADENA, Calif. - In a show of technological wizardry, the robotic explorer Curiosity blazed through the pink skies of Mars, steering itself to a gentle landing inside a giant crater for the most ambitious dig yet into the Red Planet's past.
A chorus of cheers and applause echoed through the NASA Jet Propulsion Laboratory on Sunday night after the most high-tech interplanetary rover ever built sent a signal to Earth. Minutes earlier, it had been in a harrowing plunge through the thin Mars atmosphere.
It was NASA's seventh landing on Earth's neighbor; many other attempts by the U.S. and other countries to zip past, circle or set down on Mars have gone awry.
The arrival was an engineering tour de force, debuting never-before-tried acrobatics packed into "seven minutes of terror" as Curiosity sliced through the Martian atmosphere at 13,000 mph.
In a Hollywood-style finish, cables delicately lowered the rover to the ground at a snail-paced 2 mph. A video camera was set to capture the most dramatic moments - which would give earthlings their first glimpse of a touchdown on another world.
The extraterrestrial feat injected a much-needed boost to NASA, which is debating whether it can afford another Mars landing this decade. At a budget-busting $2.5 billion, Curiosity is the priciest gamble yet, which scientists hope will pay off with a bonanza of discoveries.
Over the next two years, Curiosity will drive over to a mountain rising from the crater floor, poke into rocks and scoop up rust-tinted soil to see if the region ever had the right environment for microscopic organisms to thrive. It's the latest chapter in the long-running quest to find out whether primitive life arose early in the planet's history.
Curiosity's first stop will be Gale Crater, which may have once contained a lake. After at least a year, the rover will arrive at Mount Sharp, in the center of the crater. The rover will drive up the mountain examining layers of sediment. This process is like looking at a historical record because each layer represents an era of the planet's history, scientists say.
The phenomenon of sedimentary layers is remarkably similar to what is seen on Earth, in California's Death Valley or in Montana's Glacier National Park, says John Grotzinger, chief scientist of the Mars Science Laboratory mission.
Rocks and minerals found on Earth are different than on Mars, but the idea of a mountain made of layers is familiar to scientists. Unlike on Earth, however, Mars has no plate tectonics, so the Martian layers are flat and not disrupted as they would be on Earth. That also means that Mount Sharp was formed in a different way than how mountains are created on Earth -- no one knows how.
In these layers, scientists are looking for organic molecules, which are necessary to create life. But even if Curiosity finds them, that's not proof that life existed -- after all, these molecules are found in bus exhaust and meteorites, too, says Steve Squyres, part of the Mars Science Laboratory science team.
If there aren't any organics, that may suggest there's something on the planet destroying these molecules, says James Wray, assistant professor of Earth and atmospheric sciences at the Georgia Institute of Technology and collaborator on the Curiosity science team. But if Curiosity detects them, Wray said, that might help scientists move from asking, "Was Mars ever habitable?" to "Did Mars actually host life?"
"A successful landing will grant a huge breath of relief to the entire Mars science community tonight," Wray said in an e-mail. "And it will certainly keep NASA at the forefront of Mars exploration for at least the next few years."
Liquid water is not something scientists expect to be apparent on Mars because the planet is so cold and dry, Squyres said. If the planet does harbor liquid water today, it would have to be deep below the surface, perhaps peeking out in a few special places, but not likely to be seen by Curiosity, Squyres said.
It's hard to know how long ago liquid water would have been there because there's no mechanism to date the rocks that rovers find on Mars, Squyres said.
Evidence from the spacecraft NASA has sent to Mars so far suggests that the "warm and wet" period on Mars lasted for the first billion years of the planet's history.
"In order to create life, you need both the right environmental conditions -- which includes liquid water -- and you need the building blocks from which life is built, which includes organics," Squyres said. The Mars Science Laboratory is a precursor mission to sharper technology that could do life detection, Grotzinger said.
There aren't specific molecules that scientists are looking for with Curiosity. The attitude is: "Let's go to an interesting place with good tools and find out what's there," Squyres said.
"7 Minutes of Terror"
The voyage to Mars took more than eight months and spanned 352 million miles. The trickiest part of the journey? The landing. Because Curiosity weighs nearly a ton, engineers drummed up a new and more controlled way to set the rover down. The last Mars rovers, twins Spirit and Opportunity, were cocooned in air bags and bounced to a stop in 2004.
The plans for Curiosity called for a series of braking tricks, similar to those used by the space shuttle, and a supersonic parachute to slow it down. Next: Ditch the heat shield used for the fiery descent.
And in a new twist, engineers came up with a way to lower the rover by cable from a hovering rocket-powered backpack. At touchdown, the cords cut and the rocket stage crashed a distance away.
The nuclear-powered Curiosity, the size of a small car, is packed with scientific tools, cameras and a weather station. It sports a robotic arm with a power drill, a laser that can zap distant rocks, a chemistry lab to sniff for the chemical building blocks of life and a detector to measure dangerous radiation on the surface.
It also tracked radiation levels during the journey to help NASA better understand the risks astronauts could face on a future manned trip.
After several weeks of health checkups, the six-wheel rover could take its first short drive and flex its robotic arm.
The landing site near Mars' equator was picked because there are signs of past water everywhere, meeting one of the requirements for life as we know it. Inside Gale Crater is a 3-mile-high mountain, and images from space show the base appears rich in minerals that formed in the presence of water.
Previous trips to Mars have uncovered ice near the Martian north pole and evidence that water once flowed when the planet was wetter and toastier unlike today's harsh, frigid desert environment.
Curiosity's goal: to scour for basic ingredients essential for life including carbon, nitrogen, phosphorous, sulfur and oxygen. It's not equipped to search for living or fossil microorganisms. To get a definitive answer, a future mission needs to fly Martian rocks and soil back to Earth to be examined by powerful laboratories.
The mission comes as NASA retools its Mars exploration strategy. Faced with tough economic times, the space agency pulled out of partnership with the European Space Agency to land a rock-collecting rover in 2018. The Europeans have since teamed with the Russians as NASA decides on a new roadmap.
Despite Mars' reputation as a spacecraft graveyard, humans continue their love affair with the planet, lobbing spacecraft in search of clues about its early history. Out of more than three dozen attempts - flybys, orbiters and landings - by the U.S., Soviet Union, Europe and Japan since the 1960s, more than half have ended disastrously.
A Hopeful Future
Curiosity is supposed to last for two years on Mars, but it may operate longer -- after all, Spirit and Opportunity, which arrived on Mars in 2004, were each only supposed to last 90 Martian days. Spirit stopped communicating with NASA in 2010 after getting stuck in sand, and Opportunity is still going.
"You take what Mars gives you," said Squyres, also the lead scientist on the Mars Exploration Rover Mission, which includes Spirit and Opportunity. "If we knew what we were going to find, it wouldn't be this much fun."
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