That’s Comet 67P/Churyumov–Gerasimenko. It’s the one that scientists hope to put a lander on in November (three months away!). To their surprise, though, it’s kicking out dust while still very distant from the sun, much more distant than anticipated. The expectation was that as it got closer to the sun the radiation pressure would cause gas, ice and dust to stream off the comet in ever greater quantities. But it’s already doing so (in minute amounts, to be sure).

What else are we going to learn from this experiment?