Here’s where Curiosity comes in with its drills and scoops, sample canisters, analyzers and labs. The intended landing site is Gale Crater, a very large pit on Mars that offers ideal landing conditions and prime science territory. Vast areas of Gale are nice and flat, a great place for our rover to touch down. Those areas are also very low-lying, which is important when you land on Mars: in order for your parachutes to even work you have to have a sufficiently dense atmosphere, so the lower your landing terrain, the thicker the atmosphere, the more your chutes will slow you down. In fact, it’s pretty much impossible to land on one of Mars’ taller mountains, like the extinct volcano Olympus Mons – the atmosphere is simply too thin!
So, we go for the lowest altitude we can find. Gale Crater – like many impact craters – also has a fabulous central mound that resulted from the impact and thus presents a great opportunity for some one-the-spot geology. Moreover, the northwestern slope of the central mound has all kinds of interesting layers of rock, as Mars Global Surveyor and other orbiting spacecraft have discovered, so all that Curiosity needs to do is drive over, take a sample, drive up higher to the next layer, take more samples, and so on. Most of those layers of rock are within a manageable slope that the rover can climb without tipping over, as there are several canyons that provide access.
So, we have a nice thick atmosphere, our chutes can function, but it’s of course not enough for a landing. There is a heat shield to protect the spacecraft from the enormous heat generated during atmospheric entry. This heat shield must be jettisoned at the proper time so the rover can be readied. It will unfurl its wheels and closer to the surface a structure called a “sky crane”, which looks like a big four-legged spider with the rover attached to its belly, will fire rockets to slow down and halt its descent. It will then gently lower the rover to the surface on ropes. The ropes must then be cut and the sky crane will fly off and crash-land somewhere at a safe distance.