How will Curiosity actually get free of the spacecraft that's carried it to Mars?
Curiosity, as Mischna noted, is too big to rely on airbags to soften its landing. Instead, the spacecraft itself will use a sky crane to connect the rover to the Martian surface. The method relies on a system of steerable rockets, located on the underbelly of the spacecraft, that will both slow the vehicle and mitigate the effects of any horizontal winds it might encounter. Once the craft has slowed to zero velocity, the sky crane system will lower Curiosity on a bridle that will extend about 25 feet to the ground. (Curiosity will actually, at first, be attached to its craft via three nylon -- nylon! -- tethers, along with an "umbilical cord" to provide power and a communication connection.)
The craft's landing system will place the rover on its wheels, allowing mission controllers to check its systems and make sure that it survived the landing intact and ready to roll. As soon as touchdown is detected, though, the bridle will be cut using pyrotechnic cutters -- and the craft itself will launch away from Curiosity's landfall site, crash-landing at a safe distance from the rover.
Will the landing really be as dramatic as everyone is saying?
Yes. Mostly because there are so many ways that it could go wrong, and so many aspects of Curiosity's fate, at this point, that are out of human control. Curiosity's planned Martian descent is "the most daring landing ever attempted on an alien world," as The Guardian put it, because the descent itself is alien to us. All we can do, at this point, is watch.
Speaking of ... can I watch the landing?
You can! Right here. Or here. Or here. (And you can also get updates from the perky little rover itself via -- natch -- its perky little Twitter feed.)
Whatever you see, though, won't be happening in real time: For this mission, there's a 14-minute communications gap between Earth and Mars, meaning that even the scientists who created Curiosity will be spectators in the landing itself. The landing's success, or failure, will be determined by the interaction between earthly computers and Mars's gravitational pull. And while the landing itself is scheduled to occur at 1:30 a.m. Eastern, officials have cautioned that confirmation of the touchdown could take several hours -- or even several days. During which time, we'll just have to wait. And hope.
So what if something goes wrong?
Something could go wrong! And really easily. There are multiple steps that coordinate iteratively over the course of Curiosity's "seven minutes of terror." If any of those doesn't go precisely according to plan, the entire mission will be moot. "Failure could set back American-led Mars explorations for years," The New York Times notes.
Then again, though: If Curiosity fails, it won't be the first time NASA has experienced a setback in its overall mission to Mars. In 1999, infamously, the agency lost a Mars orbiter due to confused measurements between metric and English systems. But NASA has also had great successes with rover exploration of the Red Planet. The rover Opportunity, launched in 2003 and landed on Mars in 2004, is still actively exploring the Red Planet. In 2010, NASA finally lost communication with Opportunity's twin rover, Spirit, which, in 2009 -- after nearly five years of Martian recon -- became stuck in Mars's soft soil. So if something goes wrong with Curiosity, "we'll pick ourselves up, dust ourselves off," Doug McCuistion, NASA's Mars exploration program director, told reporters at a news conference on Saturday. "This will not be the end."