Surprisingly, the first color picture of comet 67P/Churyumov-Gerasimenko taken by the ESA’s Rosetta spacecraft depicts it even darker and more monochrome than previously expected. This picture puzzled many comet fans that thought a previous picture of the comet, in a reddish hue, would be the closest to reality.
The earlier image was released about one week ago and showed the 67P comet in a reddish color. Sebastien Besse, a European Space Agency (ESA) researcher, said that this image might not be accurate since it is a RGB image. RGB images can be easily altered by the camera’s settings to provide each channel with a specific color. Camera filters usually enhance the color of a specific element on the comet such as minerals or molecules.
In RGB pictures, scientists can use whatever combination of filters they want leading to images entirely different from the ones a human eye perceives.
Mr Besse also warned 67P’s fan not to give too much credit to the reddish picture since it was just “an early product.”
The final product, however, was taken this week by the Rosetta spacecraft’s camera called Osiris. Rosetta spacecraft is currently orbiting 67P/Churyumov-Gerasimenko comet after successfully dropping last month the Philae probe onto its surface.
“We like to refer to Osiris as the eyes of Rosetta,”
Dr Holger Sierks, one of Osiris’ investigators, said.
Osiris camera photographed the comet using three different filters of red, green, and blue. These filters were later assembled to form a complete image of the comet that was expected to show the world what was 67P’s real color. However, the results disappointed a lot of people – the object was “as black as coal.”
Researchers said that they had to use three color layers to form the picture because Osiris doesn’t operate like the human eye. The three different shots were not easy to get since Rosetta spacecraft was continuously moving along the comet, while the comet was also spinning during its flight. So, Osiris team had to make some tight changes in angle every now and then.
The final image looks like similar grayscale pictures of 67P.
“As it turns out, 67P looks dark gray, in reality almost as black as coal,”
Dr Sierks also said.
However, the current image of the comet we all were able to see doesn’t seem too dark. ESA scientists said that this picture was edited to allow us to see the comet’s features.
All in all, 67P true colors were not a surprise for Rosetta’s scientists. They said that most of the small bodies in our solar system they had studied were gray by default. If 67P had had some water on its surface, scientists said, it would have had a more bluish color.