One of the rarest and most exciting events in space exploration is when we land on another celestial body and achieve a boots-on-the-ground view of an alien world. Europe's Rosetta mission is now poised to add another extraterrestrial landfall to that very short list, and top a new list as it becomes the first mission to land a probe on a comet.
Since we began traveling space in 1957 we've only landed on a handful of celestial bodies: Earth's Moon, Mars and Venus, Saturn's moon Titan, and the asteroid Eros (which was less a true landing than a low-speed crash while taking pictures on the way down).
The European Space Agency's (ESA) Rosetta spacecraft, launched in 2004, is now on a final approach to the comet 67P/Churyumov-Gerasimenko for an August 6th rendezvous, and already the preliminary pictures it has taken are revealing that this comet may be a greater treasure trove of information than expected.
Pictures show what appears to be a double-lobed nucleus, a possible "contact binary," a configuration we've seen in a few other comets and some asteroids. The events that shape this style of comet nucleus are not known—because we've never seen it happen, and so far have not examined such an object up close and in detail...something that may be about to change.