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'Seven minutes of terror': Mars rover landing will be a nail-biter

Scientists are utilizing a complicated new 'sky crane' technique for landing the car-sized Curiosity rover on Mars Monday. The hope is that the good luck NASA has had with Mars missions will hold up.  

By Staff writer / August 3, 2012

NASA's Hubble Space Telescope snapped this shot of Mars on Aug. 26, 2003, when the Red Planet was 34.7 million miles from Earth. The picture was taken just 11 hours before Mars made its closest approach to us in 60,000 years.

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NASA calls it "seven minutes of terror" – the final minutes that the one-ton Mars rover Curiosity must survive to cap an eight-month interplanetary cruise.

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Using a unique "sky crane" approach, a rocket-powered descent module will gently ease a tethered Curiosity onto the red planet's surface, then release the rover and fly off to crash at a safe distance from the landing site.

It's a method that will present more than its share of nail-biting moments. Indeed, at press briefings and in messages to their staffs, NASA managers have tried to underscore just how risky this venture is.

IN PICTURES: Exploring Mars

While using any new technology for the first time on such a high-profile space mission carries risks of failure, if history is any guide, the odds for success may be somewhat higher than NASA publicly acknowledges.

Slated to arrive on the surface of Mars at 1:31 a.m. Eastern Daylight Time Monday, the rover is the most expensive, scientifically ambitious robotic craft humans have ever tried to place on another planet.

The goal of the $2.5-billion mission is to determine if Gale Crater and its central summit, informally known as Mt. Sharp, once presented an environment that at least simple forms of life could have called home.

Humanity's track record for Mars missions isn't stellar, James Green, NASA director of planetary science, suggested in an email posted July 29 on the website planetarynews.com.

Since 1960, when the first attempt at a Mars flyby was made by the Soviet Union, "the historical success rate at Mars is only 40 percent," he wrote.

That figure, however, includes all space-faring nations, such as Russia, pre- and post-Soviet collapse, which is 0 for 19, most recently with the loss of last year's Phobos-Grunt mission to study the moons of Mars. Out of the 18 mission NASA lists with Mars as the destination or as the main target for a flyby, the agency has a batting average of .730. Of the attempts at landing spacecraft on the surface, beginning with the Viking missions in 1975, the agency is six for seven.

"Getting onto the surface of Mars safely is hard," says Mark Lemmon, a planetary scientist at Texas A&M University in College Station.

How hard? Ask him about Mars Polar Lander, which was lost on landing in December 1999. He was on the science team for the lander, one of several recent Mars missions on his resume.

"I was slightly emotionally scarred by that experience," he says.

With Curiosity "I think our chances are good," he adds. "I've seen people who thought this was a scary approach to Mars exploration look at it in detail and come away and say: This is actually a really good idea."

This is not the first time engineers have reached outside the box for a Mars mission. Sixteen years ago NASA dropped its first rover onto Mars using an unorthodox method – encasing it in a cocoon of inflatable air bags.

Parts of the delivery system looked much like Curiosity's. At a predetermined altitude above Mars, a rocket-equipped descent module lowered Sojourner Truth and its landing platform via cables far enough to allow the rover's protective air bags to inflate. The module cut the cables, and the rover in its cocoon dropped to the surface, bouncing along the surface with ever smaller hops until it came to rest.

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