Today is a historic day for solar system exploration. The European Space Agency spacecraft Rosetta ended 10 years of sailing through the solar system to come to its destination, cosmic spitting distance from comet 67P/Churyumov-Gerasimenko.
Rosetta's path through the solar system was circuitous, using three gravity assisted flybys of Earth and one of Mars to build speed and get on the proper course to meet the comet. But it's finally there at the comet's current location about 405 million km...
