Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 - |
Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 - |
Nov 14 2014, 05:17 AM
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Senior Member Group: Members Posts: 2087 Joined: 13-February 10 From: Ontario Member No.: 5221 |
I think I heard it mentioned during the press conference today, (I can't find it now), about Rosetta itself possibly landing eventually, similar to what NEAR did at the end of the main mission at Eros? Since it's not like there's anywhere else to go with the remaining delta-v left by the end of 2015, and sunlight levels and activity starting to drop after perihelion, and the low gravity makes the difference between orbiting and 'landing' trivial. The whole thing would weigh a kilo or two, right?
Obviously there's a few more pressing concerns right now, but it's something to eventually think about. |
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Dec 15 2014, 09:59 PM
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Junior Member Group: Members Posts: 81 Joined: 10-August 12 From: Kingston, Ontario, Canada Member No.: 6534 |
Could it also be that the neck region is occluded by the two lobes so that less dust and other material contributing to the dark colour is able to aggregate on the surface as the comet travels through interplanetary space? Admittedly, I have little expertise in the science of comet formation so that might be nonsensical (ie. is the surface colour even expected to be due to such aggregation?).
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Dec 16 2014, 01:48 PM
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
Could it also be that the neck region is occluded by the two lobes so that less dust and other material contributing to the dark colour is able to aggregate on the surface as the comet travels through interplanetary space? Admittedly, I have little expertise in the science of comet formation so that might be nonsensical (ie. is the surface colour even expected to be due to such aggregation?). I think, we've to go back to or even before the formation of our solar system to get most of the interstellar dust the comet is made of. The net accumulation of interplanetary dust on the present orbit is probably much less than dust ejection. Therefore the currently accumulated dust on the surface - although originally material of the protoplanetary disk - has more likely been material of the comet than been collected recently from interplanetary space. Exposure to radiation (solar and galactic) might be less in the neck region, leading to a different chemistry over long periods of time. But surface dust is probably reworked due to activity, such that this kind of radiation-induced differences should be hard to detect. An approach based on activity and varying settlement of cometary dust will probably be more promising. The dark surface color is (very likely) mostly due to carbon-rich compounds (somewhat similar to soot or asphalt), and to the fine-grained (almost fractal) surface structure (rough surfaces tend to be darker than smooth ones). Grain size influences color. Structural colors (in contrast to pigment colors) are caused by surface structures the size about the wavelength of visible light. Areas on the surface of the comet may vary in their preferred accumulation and ejection of grains of a certain size or structure, and vary in color by this mechanism. Pigmentation (chemical composition) may vary for a similar reason. |
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