The presence of ice on Comet Churyumov-Gerasimenko is no surprise. Its very cold on the rock racing through space – colder than your worst dreams might imagine. At http://phys.org/print345465855.html … the ice, or what looks like water ice, is located in the neck region, between the head and the body of the comet. This is the region where jets of dust and gas are issuing from – creating the neck in the process. The interpretation is therefore not without a certain amount of doubt although frozen water must be present as water vapour has been seen to jet off the comet.
When seen with the human eye Comet Churyumov-Gerasimenko is grey all over – really rather dull. Rosetta's imaging system filters colours in order to delineate differences in reflectivity, and differences that might occur on the surface of the comet. In fact, the same regions are filtered with different colours at different times. The colour filter system provides clues to what is on the surface and what the surface is made from – or emitting. The recent red images of the comet that spread around the Internet come from colour filtering.