That point will be about 185 million kilometres from the Sun, between the orbits of Earth and Mars.
The images above (top) show how the frozen ices on the comet sublimate as its surface layers are gently warmed the closer it gets to the Sun. The escaping gas carries streams of dust out into space, and together these slowly expand to create the comet’s fuzzy atmosphere, or coma.
This process increases the closer to the Sun the comet gets when pressure from the solar wind causes some of the materials to stream out into long tails – one made of gas, the other of dust.
The comet’s coma will eventually span tens of thousands of kilometres, while the tails may extend hundreds of thousands of kilometres, and both will be visible through large telescopes on Earth.
The montage of 18 images shows off the comet’s activity from many different angles as seen between 31 January (top left) and 25 March (bottom right), when the spacecraft was at distances of about 30 to 100 kilometres from the comet. At the same time, Comet 67P/Churyumov-Gerasimenko was at distances between 363 million and 300 million kilometres from the Sun.
All these images have been published before, except for the one from 25 March, which we have enlarged above.
You can also read the Cosmos feature on the historic mission, All set for our first comet landing.
Bill Condie is a science journalist based in Adelaide, Australia.
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