Enceladus Plume Search, Nov. 27 |
Enceladus Plume Search, Nov. 27 |
Nov 24 2005, 04:01 PM
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Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
Interesting item in the science plan kernel (S16) just released to the NAIF website:
OBSERVATION_ID: S1629 SEQUENCE: S16 OBSERVATION_TITLE: Plume Search SCIENCE_OBJECTIVE: Hope to detect/observe plumes, whether from volcanic activity or geysers. OBS_DESCRIPTION: Point and stare. SUBSYSTEM: ISS PRIMARY_POINTING: ISS_NAC to Enceladus (0.0,5.0,0.0 deg. offset) REQUEST_ID: ISS_018EN_PLUMES001_PRIME REQUEST_TITLE: ENCELADUS Geyser/Plume Search REQ_DESCRIPTION: 1;ENCELADUS Geyser/Plume Search 1x1xNPp -- 3 different exposures BEGIN_TIME: 2005 NOV 27 19:00:00 UTC END_TIME: 2005 NOV 27 20:00:00 UTC -------------------- |
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Dec 1 2005, 11:28 AM
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
Ugordan: "....but haven't there been some mentions recently about ammonia being destroyed by UV sunlight practically immediately so that's one of the reasons it hasn't been detected yet? ..."
I've pointed that out, because NH3 is split by the far more abundant long-wavelength UV than H20, split by much lower intensity short-UV. (In addition, NH3 in an atmosphere like primordial Titan doesn't form the equivalent of an Ozone layer that protects the cold-trapped stuff in the atmosphere below.) But this pretty much only applies to solid moon surfaces where exposure times are generally *LONG*. Given plausible ice+ammonia compositions for frosts, and the solar spectrum, somebody with the skills and knowledge can (and I'd assume has) published detectability lifetimes for ammonia containing surface frosts in the outer solar system, but I've never seen numbers. Something like the plumes is entirely different. I can imagine the stuff spread out along the E-ring to have lost NH3 to photolysis, but I can't imagine that stuff in the Enceladus diffuse plume or the narrower jets to be severely ammonia depleted. I have total confidence that the Cassini mission will try during primary and extended missions to get the best info they can on plume composition and trace vapor/ice limits. |
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