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New Huygens descent views, New views of Huygens on the way down to Titan |
 May 4 2006, 04:35 PM
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Junior Member  Group: Members Posts: 73 Joined: 14-June 05 From: Cambridge, MA Member No.: 411  |
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May 18 2006, 01:47 PM
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#2
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 Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
I think someone is using a definition of scale height based on 1 over 10 instead of 1 over e. By my reckoning the scale height for Titan is only about 2.5 x Earth's whichever definition you use.
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May 18 2006, 02:17 PM
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#3
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 Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
QUOTE (ngunn @ May 18 2006, 02:47 PM)  I think someone is using a definition of scale height based on 1 over 10 instead of 1 over e. By my reckoning the scale height for Titan is only about 2.5 x Earth's whichever definition you use. Good point. I went digging and found a formula to check it and realised just how temperature sensitive pressure scale height is. Plugging in the numbers into H=kT/mg (Scale height = Boltzman const * Temperature/(molecular mass of atmosphere * gravitational acceleration) gives a scale height of 20km at the surface (T=94K) however ths Huygens atmospheric temperature profile shows the temperature varying from around 75K to 210K depending on altitude - that seriously mucks around with scale height, pushing it from a minimum of 16 to a maximum of 46. All I can say is good luck to the atmospheric modelling folks. 
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May 18 2006, 03:02 PM
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#4
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
QUOTE (helvick @ May 18 2006, 03:17 PM) Good point. I went digging and found a formula to check it and realised just how temperature sensitive pressure scale height is. Plugging in the numbers into H=kT/mg (Scale height = Boltzman const * Temperature/(molecular mass of atmosphere * gravitational acceleration) gives a scale height of 20km at the surface (T=94K) however ths Huygens atmospheric temperature profile shows the temperature varying from around 75K to 210K depending on altitude - that seriously mucks around with scale height, pushing it from a minimum of 16 to a maximum of 46. All I can say is good luck to the atmospheric modelling folks. Look again. The big temperature swings are all well above the tropopause and hence well above the 1 over e point. In fact the temperature in the first 20km is actually lower than the surface temperature, which would tend to LOWER the 1 over e point slightly from the simplistic value based on constant T. The upper atmosphere is indeed much inflated due to both temperature and inverse square law for g, but that doesn't affect the lower atmosphere up to the 1 over e point. |
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May 18 2006, 03:33 PM
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#5
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
Yep - you're dead right there. The scale height in the region under discussion is 20km or lower which puts the 0.1 bar level at 24-30km.
Ah well - at least I have a better understanding of it now - it's good to be wrong. |
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jsheff New Huygens descent views May 4 2006, 04:35 PM
volcanopele I started a new thread with this info, so I am jus... May 4 2006, 04:41 PM
helvick QUOTE (volcanopele @ May 4 2006, 05:41 PM... May 4 2006, 05:41 PM Rakhir ESA press release
http://www.esa.int/esaSC/SEMKVQ... May 4 2006, 04:45 PM ljk4-1 How long before there is a similar print on Titan?... May 4 2006, 05:21 PM JRehling QUOTE (ljk4-1 @ May 4 2006, 10:21 AM... May 4 2006, 06:05 PM paxdan awesome doesn't do justice. It is a hell of a ... May 4 2006, 06:43 PM ElkGroveDan QUOTE (ljk4-1 @ May 4 2006, 09:21 AM... May 4 2006, 10:18 PM volcanopele A high-resolution version of the movie (both silen... May 4 2006, 06:00 PM helvick QUOTE (volcanopele @ May 4 2006, 07:00 PM... May 4 2006, 09:34 PM Richard Trigaux What is interesting is that at last they suceeded ... May 5 2006, 06:12 AM The Messenger http://photojournal.jpl.nasa.gov/catalog/PIA08117
... May 8 2006, 04:12 AM BruceMoomaw Most of those "exposures" were simply sp... May 8 2006, 05:26 AM Matt QUOTE (ljk4-1 @ May 4 2006, 06:21 PM... May 9 2006, 08:17 PM Bob Shaw QUOTE (Matt @ May 9 2006, 09:17 PM) J, al... May 9 2006, 08:44 PM ugordan Looking at another thread showing the surface of V... May 15 2006, 07:19 AM The Messenger QUOTE (ugordan @ May 15 2006, 01:19 AM) I... May 15 2006, 01:57 PM ngunn While we're still free to guess here's min... May 15 2006, 02:56 PM Bob Shaw QUOTE (ngunn @ May 15 2006, 03:56 PM) Whi... May 15 2006, 03:06 PM ngunn QUOTE (Bob Shaw @ May 15 2006, 04:06 PM) ... May 15 2006, 03:32 PM BruceMoomaw Bar-Nun's pre-landing lab tests repeatedly con... May 16 2006, 01:34 AM The Messenger QUOTE (BruceMoomaw @ May 15 2006, 07:34 P... May 17 2006, 04:47 AM ngunn Some more interesting questions:- How much of the... May 16 2006, 08:13 AM BruceMoomaw It may clear it to some extent -- but the raindrop... May 17 2006, 04:14 AM ngunn QUOTE (BruceMoomaw @ May 17 2006, 05:14 A... May 17 2006, 08:29 AM BruceMoomaw I would now be very hesitant to say that we didn... May 18 2006, 01:00 AM ngunn QUOTE (BruceMoomaw @ May 18 2006, 02:00 A... May 18 2006, 09:44 AM Bob Shaw QUOTE (ngunn @ May 18 2006, 10:44 AM) Tha... May 18 2006, 10:55 AM Bob Shaw Here are the images from today's New Scientist... May 18 2006, 02:27 PM djellison QUOTE (Bob Shaw @ May 18 2006, 03:27 PM) ... May 18 2006, 03:35 PM BruceMoomaw First, on the altitude of Titan's clouds, see ... May 18 2006, 11:55 AM ngunn Fascinating stuff, thanks Bruce. Just one nit-pick... May 18 2006, 12:27 PM helvick QUOTE (ngunn @ May 18 2006, 01:27 PM) Fas... May 18 2006, 01:03 PM ngunn QUOTE (helvick @ May 18 2006, 04:33 PM) Y... May 18 2006, 04:00 PM remcook The scale height changes with altitude, since temp... May 18 2006, 02:02 PM BruceMoomaw Yep, I did get the scale height figure for Titan f... May 18 2006, 02:13 PM The Messenger Another curiosity in this report is the electrical... May 18 2006, 04:16 PM BruceMoomaw Quoting the HASI team's article in the Dec. 8 ... May 19 2006, 12:23 PM BruceMoomaw Here's the peculiarity noted after landing by ... May 19 2006, 01:03 PM ljk4-1 QUOTE (BruceMoomaw @ May 19 2006, 09:03 A... May 19 2006, 07:24 PM BruceMoomaw QUOTE (ljk4-1 @ May 19 2006, 07:24 P... May 19 2006, 09:49 PM BruceMoomaw And here's some more recent stuff on the last-... May 19 2006, 01:18 PM ngunn The only probe-induced event I can think of is dow... May 19 2006, 02:17 PM The Messenger It is curious that there was not a significant cha... May 19 2006, 08:55 PM Bob Shaw QUOTE (The Messenger @ May 19 2006, 09:55... May 19 2006, 09:05 PM edstrick Obviously, the permittivity change and the gas emi... May 20 2006, 10:34 AM BruceMoomaw Either that, or that penguin who turns up in a cou... May 20 2006, 04:18 PM The Messenger I ran the permittivity question past a guru, who h... May 22 2006, 08:25 PM JTN An idle query:
In the narrated video release which... Jun 17 2006, 08:39 PM tfisher QUOTE (JTN @ Jun 17 2006, 03:39 PM) An id... Jun 18 2006, 01:37 PM edstrick Since the sun is minimally (if at all) visible at ... Jun 19 2006, 08:40 AM ngunn I've spent some time trying to imagine how a h... Jun 19 2006, 12:52 PM ugordan I guess it all comes down to contrast. The sun is ... Jun 19 2006, 01:17 PM ngunn QUOTE (ugordan @ Jun 19 2006, 02:17 PM) S... Jun 19 2006, 01:55 PM The Messenger QUOTE (ngunn @ Jun 19 2006, 07:55 AM) I... Jun 19 2006, 03:46 PM ngunn QUOTE (The Messenger @ Jun 19 2006, 04:46... Jun 19 2006, 04:22 PM djellison It's a cloud day outside - your average large ... Jun 19 2006, 02:07 PM climber Dear All,
I received recently my monthly copy of ... Oct 10 2006, 08:53 PM djellison Is it the same as this:
http://sci.esa.int/science... Oct 10 2006, 09:04 PM climber QUOTE (djellison @ Oct 10 2006, 11:04 PM)... Oct 10 2006, 09:22 PM |
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