Those who have been observant while looking at the images of Comet 67P/Churyumov-Gerasimenko, which were released by the European Space Agency (ESA) since Rosetta started taking pictures of the comet earlier this year, may have noticed that the photos are all in black and white.
For the first time, however, Rosetta had a color photo of the comet it has been closely following since August this year. In the true-color photo, comet 67P has hues that resemble that of a reddish brown clay.
The image was released along with an abstract for the presentation "Color Variegation on 67P/Churyumov-Gerasimenko," which is set to be shown at the upcoming American Geophysical Union conference in San Francisco on Dec. 18.
Rosetta, which was tasked to conduct a close range study of comet 67P in the hopes it could shed more light on the history of the solar system, used its scientific imaging system Optical, Spectroscopic, and Infrared Remote Imaging System, or OSIRIS, onboard to create the true-color photo of the comet.
The OSIRIS dual camera is made up of the Narrow Angle Camera (NAC) and the Wide Angle Camera (WAC) that allow it to take high-resolution images of comet 67P and capture wavelengths of lights that are not visible to the human eye.
To come up with the true-color photo, the instrument combined images from its blue, orange and green filters; the reason the image is blurred has something to do with the comet moving between exposures.
It should be noted, however, that the color photo does not necessarily show the true color of comet 67P as it could be seen from the naked eye. The ESA had earlier described the comet to be blacker than coal.
Previous black and white images of the comet that were released by ESA were taken by Rosetta's navigation camera (NAVCAM). The space agency likewise pointed out that these gray scale images do not accurately show the actual color of the comet.
"The images, taken in black-and-white, are grey-scaled according to the relative brightness of the features observed, which depends on local illumination conditions, surface characteristics and composition of the given area," the ESA said.
Describing images of the comet taken by Rosetta while at a proximity of less than 10 kilometers from the comet's surface, the ESA said that enhancements were made to emphasize and bring out certain features and areas.