Comet Churyumov-Gerasimenko, illustration. This comet (67P/Churyumov-Gerasimenko) is around 3.5 by 4 kilometres, and has a characteristic lobed structure. The European Space Agency's Rosetta spacecraft (launched March 2004) entered orbit around this comet on 6 August 2014. It carried instruments and a lander to map and study the comet's surface and core. Studying comets gives insights into conditions during the formation of the solar system some 4.6 billion years ago. This artwork shows a cutaway of the pockets of gas and ice just beneath its surface. Jets of gas and dust are emitted as the Sun causes sublimation of the ice.