The European Space Agency (ESA) announced today that Rosetta’s lander will aim to touch down on Comet 67P/Churyumov–Gerasimenko at an area called Site J. The site was chosen because, on the comet's rocky surface, it's a relatively flat spot and because it also gets plenty of light—which will be important to the lander once it switches to solar power.
Rosetta became the first artificial satellite to ever orbit a comet when it reached its destination last month. But actually landing on a comet will be another feat entirely. As the BBC’s Jonathon Amos reports, the surface of the comet is extremely rough, making finding a safe place to land extremely difficult. Then, there’s the distance between Philae and its controllers. From the BBC:
The spider-like device will hope to engage the surface at "walking pace", deploying screws and harpoons in an effort to lock itself down.
It will be a one-shot opportunity. The event will take place so far from Earth that real-time radio control will be impossible.
Instead, the process will have to be fully automated with commands uploaded several days in advance.
Site J is situated on what the ESA calls the head of the comet, while the backup site is located on the body of the comet. (Remember, Churyumov–Gerasimenko is shaped like a giant rubber duck.) On November 11, Rosetta’s lander, Philae, will be deployed to the surface of the comet in a process expected to take seven hours. Philae carries nine experiments and a drill that will be used to gather samples of the comet’s subsurface.