Official Rosetta image reveals comet's true colors

Not long ago, the Internet was speculating that Comet 67P was on the reddish side, but a new image from the European Space Agency shows the comet goes for gray.

Amanda Kooser
Freelance writer Amanda C. Kooser covers gadgets and tech news with a twist for CNET. When not wallowing in weird gear and iPad apps for cats, she can be found tinkering with her 1956 DeSoto.
Amanda Kooser
2 min read

Comet 67P looks good in gray. ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The European Space Agency's Rosetta spacecraft has snapped another portrait of the space celebrity Comet 67P/Churyumov-Gerasimenko, and this time -- for the first time -- it's in color.

Interestingly enough, it doesn't look much different than the black-and-white images we've seen in the past.

Captured by Rosetta's Osiris camera, the photo is a combination of images taken through filters centered on red, green and blue wavelengths. Those images are superimposed to give us the "color" shot.

"As anticipated, the comet turns out to be very grey indeed, with only slight, subtle colour variations seen across its surface," the ESA reports.

It's taken so long to get a color image of the comet in part due to the amount of work required to match up the three images. The images were taken in sequence, but the comet was rotating during the process.

An earlier image of Comet 67P hit the Internet about a week ago. The image is distinctly reddish, which led to a lot of speculation about what the comet would look like to the human eye. This particular image accompanies a paper presentation scheduled for December 18 at an American Geophysical Union conference in San Francisco.

Sebastien Besse, an ESA research fellow and one of the co-authors of the paper, explains why the image of a reddish comet may not be accurate when it comes to what the human eye would see.

"Images like this are RGB, and you can put what you want in each channel. Each filter of the camera is designed to enhance a specific molecule/mineral. So colour images are not necessarily representing the colour of the comet. This depends on the combination of filters you use in your RGB, and I don't know which filters are used for this image," Besse tells Crave. He cautions comet fans to not read too much into the red image, describing it as "an early product."

The ESA dives deeper into this idea: "A more-detailed first analysis nevertheless reveals that the comet reflects red light slightly more efficiently than other wavelengths. This is a well-known phenomenon observed at many other small bodies in the Solar System and is due to the small size of the surface grains. That does not, however, mean that the comet would look red to the human eye."

Combining Besse's explanation of the enhanced colors in the reddish image with ESA's official and very gray image, it looks like everyone's favorite comet is more at home with a color palette from the Dark Side.

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