At NASA they've called it "Seven Minutes of Terror" -- the white-knuckle moments as the new Curiosity rover, scheduled to land on Mars on the night of Aug. 5, goes tearing into the Martian atmosphere and, engineers hope, lands safely seven minutes later.
NASA made a computer-animated video of the landing sequence, and found it has a hit on its hands. With almost a month to go until landing, the video had already been viewed more than half a million times on YouTube alone, and it's appeared on countless other websites as well.
"We've got literally seven minutes to get from the top of the atmosphere to the surface of Mars -- going from 13,000 miles an hour to zero, in perfect sequence, perfect choreography, perfect timing," said Tom Rivellini, a NASA engineer who appears in the video.
NASA has been very good at visualizing its robotic missions, and, in fact, did similar videos (with the same title) for previous Mars landings in 2004 and 2008. But none went viral the way Curiosity's has.
The Curiosity rover, known originally as Mars Science Laboratory, is about the size of an SUV. Behind schedule and over budget, it was a decade in the making and has cost $2.5 billion. The nickname Curiosity came from a schoolchild who won a NASA contest to pick something memorable.
Because of its size, Curiosity cannot just fly to Mars and come to a stop. The protective air bags used to land previous rovers could not be made sturdy enough. So Curiosity enters the Martian atmosphere encased in a heat shield, then lets out a parachute, then fires retro rockets, then is lowered by cables from a landing stage and finally -- if it hasn't left a $2.5 billion crater in the Martian soil -- sends a signal that it's safely down.
And all this has to happen automatically. Mars will be 150 million miles from Earth on Aug. 5 -- so distant that radio commands from Earth, travelling at the speed of light, would take 14 minutes to get there.
NASA has tried to play down expectations that Curiosity could find life on Mars. But if there ever were living microbes, the rover probably has the equipment to see signs that they were there.
An earlier rover, Opportunity, is still functioning after eight years on the Martian surface. It found geological evidence that scientists say shows Mars was once warm and wet, with pools of briny water that dried up eons ago.
NASA would like to expand on that find, which is why it has sent the larger and more ambitious Curiosity rover.
But first the thing has to land safely. The engineers say 76 explosive bolts have to fire in proper sequence. They've written 500,000 lines of computer code for the ship's computers. And there is, as they dramatically put it, zero margin of error.
"When people look at it, it looks crazy," says Adam Stelzner, an engineer who laid out the landing plans, in the video. "Sometimes when we look at it, it looks crazy. It is the result of reasoned engineering thought. But it still looks crazy."