Visit to a Small Planet

Over the weekend, one of the most important events in astronomy this year took place. Last weekend, the Rosetta probe, which the ESA sent to space on an indefinite journey around the Solar System, passed by Earth a few times and Mars once, and is on it's way to a comet called 67P/Churyumov-Gerasimenko. It should arrive in about four years.


It was originally supposed to have flown to comet 46P/Wirtanen in 2011, but the launcher broke, and then stuck with a probe and nowhere to send it to, the people at the European Space Agency (ESA) started playing around and came up with a ten year mission where probe would bounce around the inner solar system seemingly randomly, and then land a tiny probe called "Philae" on the comet.

The happy accidents were the close flybys of two asteroids. The first, a small rock called 2867 Shteins, took place back in 2008, and was a success in that the camera actually caught the thing (NASA's Deep Space One missed 9969 Braille completely during a close flyby in 1999), and just a few days ago, it flew by what might be it's most important target of the entire mission: 21Lutetia, one of the largest asteroids in the main belt between Mars and Jupiter.


Lutetia, named for the city of Paris, is well over a hundred miles in diameter, (or would have, it wasn't irregular) and is thus just short of being able to be a sphere. As one can see it's a tiny world in it's own right. Scientists will be poring over the photographs and other data in preparation for the Dawn spacecraft's encounter with the much larger asteroid 4 Vesta next year, something that almost didn't happen, as Dawn was canceled just as construction of the craft was completed. Getting it back on the manifest was a bitch.

The reason is that unless there's a chance they're going to hit us, the people in charge of the money think asteroids are just not worth the bother. The chances that had the booster worked all those years ago, that anyone would even think of sending a probe to Lutetia is itself unthinkable. The probes sent to asteroids in the past were either for reasons of national pride (the Japanese Hayabusa probe studied 25143 Itokawa because it was named after a Japanese scientist), or because there was allegedly really easy to get to like Eros (it wasn't, but that's another story).


But thanks to serendipity, we have visited a brand new world few had even known was out there. Cool.