ESA’s Rosetta spacecraft is closing in for its rendezvous with a comet. It’s target has started to develop dusty veil over the last six weeks. This sequence of images presented here of comet 67P/Churyumov–Gerasimenko was taken between 27 March and 4 May, as the gap between craft and comet closed from about 5 million to 2 million km. By the end of the sequence, the comet’s dusty coma extends some 1300 km into space. By comparison, the nucleus is roughly only 4 km across, and cannot yet be resolved as more that a point of light.
The coma has developed as a result of the comet moving closer to the Sun along its 6.5 year orbit. Even though it is still more than 600 million km from the Sun, more than 4X the distance between Earth and Sun, its surface has begun to warm, and its surface ices have begun to sublimate and gas to escape from its rock–ice nucleus. As the gas escapes, it also carries a cloud of tiny dust particles out into space, which slowly expands to create the coma. As the comet comes closer to the Sun, the warming continues and activity rises. Pressure from the solar wind will eventually cause some of the material to stream out into a long tail.
Rosetta and the comet will be closest to the Sun in August 2015, between the orbits of Earth and Mars.
Image Credit: ESA