What made Curiosity's Mars landing a 'miracle?'

NASA scientists hailed the Mars rover Curiosity's flawless descent and landing as a "miracle of engineering" on Monday as they scanned early images of an ancient crater that may hold clues about whether life took hold on Earth's planetary cousin.

The one-ton, six-wheeled laboratory nailed an intricate and risky touchdown late on Sunday, much to the relief and joy of scientists and engineers eager to conduct NASA's first astrobiology mission since the 1970s Viking probes.

"We trained ourselves for eight years to think the worst all the time," Curiosity lead engineer Miguel San Martin said. "You can never turn that off."

Mission control engineers at the Jet Propulsion Laboratory near Los Angeles erupted in cheers and applause when confirmation was received that Curiosity, touted as the first full-fledged mobile science lab sent to a distant world, had landed on the Martian surface.

NASA engineers said the feat stands as the most challenging and elaborate achievement in the history of robotic spaceflight, and opens the door to a new era in planetary exploration.

President Barack Obama hailed the accomplishment as a historic "point of national pride."

The landing also marked a much-welcome success and a major milestone for a U.S. space agency beset by budget cuts and the recent cancellation of its space shuttle program, NASA's centerpiece for 30 years.

The landing was a major initial hurdle for a two-year, $2.5 billion project whose primary focus is chemistry and geology. The daredevil nature of getting the rover to Mars captured the public's imagination.

Daredevil descent 

Encased in a capsule-like protective shell, the nuclear-powered rover capped an eight-month voyage as it streaked into the thin Martian atmosphere at 13,200 miles per hour (21,243 kilometers per hour), 17 times the speed of sound.

Plunging through the top of the atmosphere at an angle producing aerodynamic lift, the capsule's "guided entry" system used jet thrusters to steer the craft as it fell, making small course corrections and burning off most of its downward speed.

Closer to the ground, the vessel was slowed further by a giant, supersonic parachute before a jet backpack and flying "sky crane" took over to deliver Curiosity the last mile to the surface.

The rover, about the size of a small sports car, came to rest as planned at the bottom of a vast impact bowl called Gale Crater, and near a towering mound of layered rock called Mount Sharp, which rises from the floor of the basin.

A trio of orbiting satellites monitored what NASA had billed as the "seven minutes of terror," but the anxiety proved to be unfounded.

From an orbital perch 211 miles (340 km) away, NASA's sharp-eyed Mars Reconnaissance Orbiter snapped a stunning and serene picture of Curiosity gracefully riding beneath its massive parachute en route to Gale Crater, located near the planet's equator in its southern hemisphere.

At 10:32 p.m. PDT on Sunday (1:32 a.m. EDT on Monday/0532 GMT on Monday) flight controllers at JPL received the equivalent of a text message from Curiosity that its journey of 352 million miles (566 million km) had ended safely.

Seven minutes later, the rover transmitted a picture, relayed by another Mars orbiter called Odyssey, showing one of Curiosity's wheels on the planet's gravel-strewn surface.

"When you see a picture of the surface of the planet with the spacecraft on it, that is the miracle of engineering," lead scientist John Grotzinger told reporters on Monday.

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