If you want a first-person sense of the intricacies involved in the landing, there's a (free) Xbox game you can play to give yourself an idea.
Where, specifically, will Curiosity land?
The rover is scheduled to make Marsfall at the Gale Crater, an impact crater that measures over 95 miles in diameter. (That would make it nearly as wide as Earth's Chicxulub crater, the impact zone of the asteroid thought to have killed the dinosaurs.) The Gale Crater was formed between 3.5 and 3.8 billion years ago. And it was chosen as Curiosity's destination because scientists believe that the sediment in the crater is likely to contain evidence that there was once a habitable environment on Mars.
Mt. Sharp, in particular -- the official name of which is Aeolis Mons, and which forms the central mound of the Gale Crater -- features an enticing series of layered rock deposits. Those layers could offer scientists a rich source of data about the Martian surface, which is also to say the Martian environment, as it's changed over time.
And there are lots of layers to explore. Mt. Sharp is comparable in height to some of the tallest mountains on Earth:
And yet the Gale Crater was actually controversial as a landing site, Wired notes. Despite Mt. Sharp's promising layers, some engineers dismissed the site as too risky for a landing. Enhanced navigational procedures, however, made NASA determine that the potential reward offered by the site would be worth the landing's considerable risk.
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?
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."
What's Curiosity going to do once it's landed?
The rover will ascend up Mt. Sharp, probing its layers for data suggesting that Mars once supported life. "We're looking for habitability, not specifically for life, but for the conditions where life might have thrived," UK Space Agency research fellow Matthew Balme told the Daily Telegraph. He added: "We want to find evidence of standing water." Project scientist John Grotzinger echoes that caveat. "Curiosity is not a life detection mission," he told The Guardian. "We're not actually looking for life; we don't have the ability to detect life if it was there."