No Really, Look at It!
You haven’t ever seen anything quite like this in your life. This is one of a continuing series of very cool images taken by the Rosetta’s NavCam imager from a distance of 9.8 kilometers from the center of the comet. What you see here is a region on the “neck” that connects the two parts of the comet together. There are rockpiles, outcrops, smooth areas, and — right in the center — what looks like dunes!
Dunes? On a comet?
That’s what many of us said when we saw this image. On one of the Facebook comet groups I’m part of, we joked around a lot about how the “spice must flow” in an obligatory “Dune” reference, but truth to tell, we were amazed to see these. What could be causing them? It’s not like there’s an atmosphere and heavy winds on the comet’s nucleus to contribute aeolian (wind-driven) forces to the comet (although there is small atmosphere, gravitationally bound to the comet. See the comments to this article for a more nuanced discussion of that).
But, think about it. We’re looking at an icy object that is getting close to the Sun (and thus is outgassing material from deep inside the comet due to the effects of solar heating). It will do more of this “mass loss” as it passes through perihelion (the closest point to the Sun) in its orbit. Outgassing comes from within the comet. So, chances are very good that those dunes are close to an outgassing vent. Or, at least, that’s what I’m hypothesizing. If so, then maybe the boulders were displaced by outgassing as well.
There’s a lot to learn about this comet, and the stream of images from Rosetta’s NavCam are paving the way to a greater understanding of just how comets change as they approach the Sun. Many thanks to the ESA folks who have been sharing images and blogging about them, and to the NavCam team for making them available. We should be seeing more from the OSIRIS team (headquartered at Max Planck Institute), which has been careful about image releases. They do have an image release program in place, so stay tuned.
In the meantime, keep an eye peeled as Rosetta prepares to launch the Philae probe to the surface on November 12, 2014. The proposed landing site, currently named “J” is the subject of a naming contest, so if you’d like to see a fancier name than a single letter, enter the contest as soon as you can.It ends at midnight GMT, October 22nd!