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Headshot of Emily Lakdawalla

An active comet, from a distance

Posted By Emily Lakdawalla

13-02-2015 13:27 CST

Topics: Rosetta and Philae, pretty pictures, comets, comet Churyumov-Gerasimenko

As I write this, Rosetta has closed to within 50 kilometers of Churyumov-Gerasimenko, on its way to a very close, 6-kilometer flyby of the comet tomorrow. ESA posted a detailed blog about the flyby today, and how it is typical of Rosetta's mission throughout 2015. But that's not what I'm writing about here. To prepare for the flyby, Rosetta traveled much farther away, allowing it to snap these amazing photos of an increasingly active comet from a great distance. Enjoy!

An active comet, from a distance

ESA / Rosetta / NavCam

An active comet, from a distance
Rosetta traveled to a distance of 124 kilometers from Churyumov-Gerasimenko to take this photo on February 6, 2015. The spacecraft was preparing for its close flyby on February 14. The most active area of the comet is the neck, but jets are visible from much of the rest of the sunlit terrain.
Comet behind a curtain

ESA / Rosetta / NavCam

Comet behind a curtain
Comet jets rise out of the shadowed neck, appearing only when they reach sunlight. Rosetta took this photo of Churyumov-Gerasimenko from a distance of 105 kilometers on February 9, 2015, as it began diving toward the comet for a close flyby on February 14. At this distance, the image is about 9.1 kilometers square.
See other posts from February 2015


Read more blog entries about: Rosetta and Philae, pretty pictures, comets, comet Churyumov-Gerasimenko


ethanol: 02/13/2015 03:25 CST

Are those jets really coming from the shadowed area in the second picture? Does the comet have enough thermal inertia to do that? I would have thought that sublimation would consume most of the energy incident on the surface, and that it would shut down pretty quickly when night sets. I guess not?

morganism: 02/14/2015 02:20 CST

I agree, just a couple centimeters of carbon dust is the best insulator in the solar system. Kinda cool that the piles of dust seem to be the emitters of the jets too. It seems like the most active areas appear to have a reflection surface near them, as if sunlight is not enough alone to initiate the activity. I wonder what the plasma field experiments are showing ? It might be possible to see if the areas most active are getting a reflection when the solar wind is protons, vs. when it is electrons.

Mac_in_Mass: 02/16/2015 04:48 CST

Hi Emily, What is the orbital period for the Rosetta craft during these fly-bys? Also, is there any estimate how fast the lander was going when it first impacted the surface? Thanks!

ethanol: 02/16/2015 07:27 CST

Man_in_Mass: Rosetta's current orbits look like something designed by a two year old with an etch-a-sketch, so it's hard to assign an orbital period to it. However the previous 26km orbit had a period around 11 days I think. I think Philae's initial touchdown was somewhere around a meter/s.

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