The Rosetta mission has been full of surprises. After launching in 2004, the spacecraft found out its target comet was duck-shaped with a candy bar-like interior, frosted in organic materials that have never before been detected on a comet.
The mission has also had its ups and downs–literally, since the Philae lander failed to anchor into the comet, bouncing half a mile high before landing in a dark crevice somewhere. Last we heard, mission scientists were still trying to establish a stable communications link with the lander, but they’ve managed to extract a surprising amount of information from it nonetheless.
For a fun overview of the mission and why the European Space Agency is going to so much trouble to study comets, watch the video at the top of the page.
Meanwhile, you can do some of your own cometary exploration using this neat little interactive from ESA.