Pasadena (California): It's the US space agency's most ambitious and expensive Mars mission yet, and it begins with the red planet arrival on Sunday of the smartest interplanetary rover ever built.
    
It won't be easy. The complicated touchdown NASA designed for the Curiosity rover is so risky it's been described as "seven minutes of terror" -- the time it takes to go from 13,000 mph (20,920 kph) to a complete stop.
    
Scientists and engineers will be waiting anxiously as the spacecraft plunges through Mars' thin atmosphere and, in a new twist, attempts to slowly lower the rover to the bottom of a crater with cables.
    
Scientists on Earth won't know for 14 minutes whether Curiosity lands safely as radio signals from Mars travel to Earth. If it succeeds, a video camera aboard the rover will have captured the most dramatic minutes for the first filming of a landing on another planet.
    
"It would be a major technological step forward if it works. It's a big gamble," said American University space policy analyst Howard McCurdy. The future direction of Mars exploration is hanging on the outcome of this USD 2.5 billion science project to determine whether the environment was once suitable for microbes to live.

Previous missions have found ice and signs that water once flowed. Curiosity will drill into rocks and soil in search of carbon and other elements.
    
Named for the Roman god of war, Mars is an unforgiving planet with a hostile history of swallowing man-made spacecraft. It's tough to fly there and even tougher to touch down. More than half of humanity's attempts to land on Mars have ended in disaster. Only the US has tasted success.
    
"You've done everything that you can think of to ensure mission success, but Mars can still throw you a curve," said former NASA Mars czar Scott Hubbard, who now teaches at Stanford University.
    
The Mini Cooper-sized spacecraft traveled eight and a half months to reach Mars. In a sort of celestial acrobatics, Curiosity will twist, turn and perform other maneuvers throughout the seven-minute thrill ride to the surface.
    
Why is NASA attempting such a daredevil move? It had little choice. Earlier spacecraft dropped to the Martian surface like a rock, swaddled in airbags, and bounced to a stop. Such was the case with the much smaller and lighter rovers Spirit and Opportunity in 2004.

(Agencies)

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