Animation of the Philae landing craft being dropped by the Rosetta spacecraft onto the surface of the comet 67P/Churyumov-Gerasimenko. Philae was carried to the comet by Rosetta, which arrived at 67P in early August 2014, after a 10.5-year journey. Rosetta became the first spacecraft to rendezvous and enter orbit around a comet, and Philae will be the first controlled landing on a comet surface. Once on the surface, it will carry out a number of experiments to determine the composition and structure of the comet, and how it interacts with the solar wind. The comet is seen to be surrounded by a coma of material, produced as the Sun heats the comet, causing volatile compounds to boil off into space. It is this coma that is the visible part of a comet from Earth.