Thursday, September 4, 2014

Venting captured from comet 67P/C-G

The European Space Agency operates the ROSETTA spacecraft that is currently enroute towards comet 67P/C-G. Due to is close proximity to the comet, the NavCam, which was capturing full frame images of the comet, it now can only capture a smaller field of view. As a result, ESA has put a task out to the imaging community to create composite images of the quarter sections of the comet they release each week.

Their first set of images were released September 4th of the images captured on the 2nd. At a distance of 56kms, four images were captured, approximately 20 minutes apart as the capture changes its angle. The comet is also rotating on its axis at this time. So not only are the images captured minutes apart, but the view of the surface features also change position.

It takes a bit of twisting and adjusting to stitch the four images together to create a cohesive composite of the combined images. But, when done correctly, you can reveal some great features on the surface, and also other interesting occurrences.

This image was combined using the 4-images, stitched together and enhanced to help the features come out. While there are currently clearer composite images completed by other individuals, this image that I processed is targeted to help highlight the current out gassing of the comet itself. Out gassing occurs when parts of the comet, has contact with the direct sunlight, causing the surface to heat up and react with trapped gases beneath the surface in the rock and ice that compose the comet. In this image, it was processed to have  +10 brightness and -12 contrast to reveal the out gassing jet that forms a plume in the "neck" of the dirty snowball. It seems to reach quite a distance, nearly the same distance as the comet is long.

click image to enlarge
To be able to see the more detail on the comet itself, the brightness was reduced -72 from the above settings. While the out-gasing plume is lost, the surface features popout and become more clear.

click image to enlarge


  1. Errol,
    if this is sublimating ice, what causes it to be so fliament like. Surely you would expect the sublimating ice to expand in all direction as soon as it was free from the surface?

  2. The issue is is that with the recent ALICE findings, there is very little ice/rock composition at the surface. The size of a plume is dependent on the gas and ice particles released in respect to its distanced to the heat/reaction source, in this case, the sun. But, the ALICE tool on Rosetta has shown much less near surface gas and ice particles then expected, which would explain the lower content. As to why its not dispersing in more of a unified direction. Well, these are jets, reacting to the heat of the sun. They will stream out the direction of lease resistance.

  3. Quote from recent Planetary Society displayed image "Rosetta took a long-exposure image with its wide-angle camera on August 2, 2014, to observe jets of dust escaping from the comet. The photo was taken from a distance of 550 kilometers. "

    You can see the OSIRIS image displayed at the Planetary Society.

    It would seem that either under long exposure, or increased brightness to the image that the jets can be seen. Now the jets might simply be dust as described in the image capture. Just commenting on the observed flume, whether it is dust, ice, or gases. Its not unheard of a comet, acting like a comet with jets. :)