As the landing day gets closer, Rosetta discovers more things about the comet. 67P/Churyumov-Gerasimenko just like other comets, looks like a lump of coal according to the European Space Agency’s Rosetta mission. The light bouncing on the said comet is around 4-6% according to experts based on “albedo” or its reflectiveness. For a better picture, our planet’s reflectiveness is 30-35%.
“The prevailing assumption is that it is the presence of organics at the surface,” says Prof Jessica Sunshine, who’s been a leading investigator on Nasa’s recent comet flybys. “You don’t need much. Just a small amount of organics can have a huge non-linear effect. “If you start throwing something that’s dark into a material that’s bright, it doesn’t take much to make that material look dark, also.”
You can see this effect here on earth, in the Arctic, where patches of ice have turned black because of the deposition of soots and other particles blown in from fires and pollution at lower latitudes. Earth is not the lightest planet in the solar system though, in fact, Venus has a light reflectiveness of 75%. The lightest object in the solar system though is the moon of Saturn, Enceladus with 99% albedo. With the Philae lander of Rosetta soon to land in comet 67P/Churyumov-Gerasimenko, scientists of Rosetta mission hopes to get information about the organic composition of the comet. Philae is equip with Cosac and Ptolemy who will be doing the analysis. Since the Rosetta mission started, mission experts have been describing the comet as a bath time yellow rubber ducks. As they get near it though, they said it looks more like a “black swan.”
“We think the comets weren’t always this dark,” says Ptolemy principal investigator Prof Ian Wright, “but after several passages around the Sun, the organics have become concentrated at the surface as ices have sublimed away.