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Pluto Atmospheric Observations: NH Post-Encounter Phase, 1 Aug 2015- TBD
scalbers
post Jul 31 2015, 02:57 PM
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QUOTE (remcook @ Jul 28 2015, 02:55 PM) *
A neat paper by Jonathan Fortney shows this ratio to scale (approximately) with sqrt(Rp/H), with Rp being the planet radius and H the scale height. Both indeed decrease this effect for Pluto.

If we assume the scale height of Pluto's atmosphere is 60km and the aerosols have the same height as the gas, then I was able to get a few numbers in the course of comparing various airmass equations. Earth would be about 39 airmasses in the horizontal and Pluto would be 6.4. These numbers would be doubled when looking at grazing incidence from space as in the NH images. I'd still like to come up with a formula for an isothermal atmosphere (exponential density decrease with height) by integrating the thin shell relationship over height and to compare this with the other formulations in Wikipedia. On the other hand, the isothermal case is within just a few percent of the homogeneous (constant density with height) case.

To check the scale height and see why it is much higher than Earth, we might evaluate this expression for Earth and Pluto:

H = kT/mg

H is scale height
T is temperature (a representative value since this varies with height)
k is Boltzmann's constant
m is molecular mass
g is gravitational acceleration

The Wikipedia link above shows this worked example for Earth:

Taking T = 288.15 K, k = 1.3806488x10-13 J/K, m = 28.96441.660510−27 kg, and g = 9.80665 m/s2 yields H = 8345m

Roughly speaking, if pluto has .07 Earth's gravity and the same T and similar m we'd get about 120km scale height. If the scale height is 60km, then the temperature would still end up being ~140K. So we can check how much the temperature increases with height over the surface value of 44K.

There are other atmosphere posts in the Near Encounter thread as well (e.g. posts #1238 and #1252).


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Posts in this topic
- scalbers   Pluto Atmospheric Observations: NH Post-Encounter Phase   Jul 31 2015, 02:57 PM
- - nprev   This topic is for discussion of data concerning Pl...   Aug 1 2015, 06:13 PM
- - Bill Harris   As noted earlier: QUOTE (Bill Harris @ Aug 3...   Aug 5 2015, 05:20 PM
- - lollipop   I meant to say that Earle and Binzel had sorted ou...   Aug 5 2015, 06:45 PM
- - Bill Harris   Even though the NH encounter increased our knowled...   Aug 5 2015, 09:40 PM
- - Herobrine   I've previously "unwrapped" the atmo...   Aug 6 2015, 08:31 PM
- - Gennady Ionov   To be seen the glow of the atmosphere due to Rayle...   Aug 11 2015, 04:08 PM
- - fredk   Are you saying that, for the geometry of that imag...   Aug 11 2015, 04:39 PM
|- - Gennady Ionov   QUOTE (fredk @ Aug 11 2015, 09:39 PM) Are...   Aug 11 2015, 04:46 PM
|- - HSchirmer   QUOTE (fredk @ Aug 11 2015, 04:39 PM) ......   Aug 12 2015, 04:04 PM
|- - Gennady Ionov   QUOTE (HSchirmer @ Aug 12 2015, 09:04 PM)...   Aug 12 2015, 04:26 PM
|- - HSchirmer   QUOTE (Gennady Ionov @ Aug 12 2015, 04:26...   Sep 24 2015, 12:58 PM
|- - Gennady Ionov   QUOTE (HSchirmer @ Sep 24 2015, 05:58 PM)...   Oct 2 2015, 06:17 PM
- - fredk   Sure, Pluto's albedo depends on position, but ...   Aug 11 2015, 05:36 PM
|- - Gennady Ionov   QUOTE (fredk @ Aug 11 2015, 10:36 PM) Sur...   Aug 11 2015, 06:12 PM
|- - fredk   QUOTE (Gennady Ionov @ Aug 11 2015, 07:12...   Aug 11 2015, 07:31 PM
|- - Gennady Ionov   QUOTE (fredk @ Aug 12 2015, 12:31 AM) But...   Aug 11 2015, 08:22 PM
|- - Bjorn Jonsson   QUOTE (fredk @ Aug 11 2015, 07:31 PM) Tha...   Aug 11 2015, 08:34 PM
||- - Gennady Ionov   QUOTE (Bjorn Jonsson @ Aug 12 2015, 01:34...   Aug 12 2015, 07:43 AM
|- - Gennady Ionov   QUOTE (fredk @ Aug 12 2015, 12:31 AM) Tha...   Aug 12 2015, 07:45 AM
- - Sherbert   The general conclusion seems to be that Pluto...   Aug 11 2015, 09:08 PM
|- - Herobrine   QUOTE (Sherbert @ Aug 11 2015, 05:08 PM) ...   Aug 11 2015, 10:21 PM
|- - JRehling   Meteors may appear over Earth at altitudes where t...   Aug 12 2015, 06:40 PM
|- - Sherbert   QUOTE (JRehling @ Aug 12 2015, 07:40 PM) ...   Aug 13 2015, 02:07 PM
|- - Gennady Ionov   QUOTE (Sherbert @ Aug 13 2015, 07:07 PM) ...   Aug 13 2015, 03:30 PM
- - fredk   About the visibility of aerosols/haze in the pre-e...   Aug 11 2015, 09:52 PM
- - Bjorn Jonsson   I have been attempting to model Pluto's atmosp...   Aug 11 2015, 10:16 PM
|- - ngunn   QUOTE (Bjorn Jonsson @ Aug 11 2015, 11:16...   Aug 11 2015, 10:32 PM
|- - scalbers   QUOTE (Bjorn Jonsson @ Aug 11 2015, 10:16...   Aug 11 2015, 11:00 PM
|- - fredk   QUOTE (Bjorn Jonsson @ Aug 11 2015, 11:16...   Aug 12 2015, 12:25 AM
|- - Gennady Ionov   QUOTE (Bjorn Jonsson @ Aug 12 2015, 03:16...   Aug 12 2015, 08:02 AM
- - remcook   Bjorn, Scalbers: why not blue? It will be blue-ish...   Aug 12 2015, 10:51 AM
- - Gennady Ionov   QUOTE (remcook @ Aug 12 2015, 03:51 PM) B...   Aug 12 2015, 11:51 AM
- - remcook   Thanks! So, the colour from your colour simula...   Aug 12 2015, 02:59 PM
- - scalbers   Good discussion of the additional factors about th...   Aug 12 2015, 04:14 PM
- - remcook   About the phase functions, here ( http://inspirehe...   Aug 12 2015, 06:05 PM
- - scalbers   Offhand, the phase function peak is more typically...   Aug 12 2015, 06:11 PM
|- - fredk   QUOTE (scalbers @ Aug 12 2015, 07:11 PM) ...   Aug 12 2015, 07:41 PM
|- - scalbers   QUOTE (fredk @ Aug 12 2015, 07:41 PM) The...   Aug 13 2015, 04:37 PM
- - nprev   Copied post from stevesilva over on the 'inter...   Aug 13 2015, 04:01 AM
- - Gennady Ionov   Thank you, Explorer, Bill!   Aug 13 2015, 04:27 AM
- - Explorer1   They do in the main post; I've copied the link...   Aug 13 2015, 04:44 AM
- - nprev   Whups! Sorry. Thanks, Explorer.   Aug 13 2015, 05:05 AM
- - Bill Harris   Why not _fix_ the bad links in the earlier post? ...   Aug 13 2015, 08:11 AM
- - Bill Harris   At Earth solar distances, we are not going to find...   Aug 13 2015, 02:37 PM
|- - Sherbert   QUOTE (Bill Harris @ Aug 13 2015, 03:37 P...   Aug 13 2015, 05:47 PM
- - Bjorn Jonsson   Here is an animation I did of the New Horizons fly...   Aug 13 2015, 05:39 PM
|- - Gennady Ionov   QUOTE (Bjorn Jonsson @ Aug 13 2015, 10:39...   Aug 13 2015, 06:22 PM
||- - Bjorn Jonsson   QUOTE (Gennady Ionov @ Aug 13 2015, 06:22...   Aug 13 2015, 07:27 PM
|- - fredk   QUOTE (Bjorn Jonsson @ Aug 13 2015, 06:39...   Aug 13 2015, 08:12 PM
|- - Bjorn Jonsson   QUOTE (fredk @ Aug 13 2015, 08:12 PM) Bea...   Aug 13 2015, 09:13 PM
|- - Gennady Ionov   QUOTE (Bjorn Jonsson @ Aug 14 2015, 02:13...   Aug 14 2015, 06:21 AM
- - scalbers   Pretty dramatic flyby from Bjorn 2 posts back. Int...   Aug 13 2015, 05:57 PM
- - ZLD   Bravo Bjorn! The animation is really great and...   Aug 13 2015, 07:48 PM
- - Herobrine   I took the code I wrote to get the value vs radius...   Aug 13 2015, 08:35 PM
- - fredk   Cool, thanks for that! About the stretching, ...   Aug 13 2015, 09:45 PM
|- - Gennady Ionov   QUOTE (fredk @ Aug 14 2015, 02:45 AM) Abo...   Aug 14 2015, 06:30 AM
- - Gennady Ionov   I calculate the average over the angle values of ...   Aug 14 2015, 12:42 PM
- - fredk   It's not clear that a psf measured from distan...   Aug 14 2015, 02:47 PM
|- - Gennady Ionov   QUOTE (fredk @ Aug 14 2015, 07:47 PM) It...   Aug 14 2015, 03:16 PM
- - fredk   Yes, absolutely, I meant it will be hard to distin...   Aug 14 2015, 04:24 PM
- - Gennady Ionov   New simulation shows New Horizons as it went into ...   Aug 23 2015, 03:47 PM
- - scalbers   Most remarkable simulations with the atmospheric s...   Aug 23 2015, 04:47 PM
|- - Gennady Ionov   QUOTE (scalbers @ Aug 23 2015, 09:47 PM) ...   Aug 23 2015, 07:01 PM
- - scalbers   Thanks for the update - I now can see the mini-moo...   Aug 23 2015, 07:36 PM
- - Gennady Ionov   It's the same bug. At one point, I added a sma...   Aug 23 2015, 08:43 PM
- - Habukaz   In case anyone missed it, the 29 June stellar occu...   Sep 8 2015, 10:12 PM
- - fredk   The press release caption for PIA19880 says we may...   Sep 14 2015, 12:22 AM
- - fred_76   Hello! Yesterday night I tried to surimpose a...   Sep 15 2015, 02:30 PM
- - scalbers   That would be interesting to see if a good enough ...   Sep 15 2015, 06:24 PM
- - Ian R   My attempt to 'unwrap' the hi-phase angle ...   Sep 15 2015, 09:38 PM
- - Herobrine   Looks like ninjas are nearby, but here's an un...   Sep 15 2015, 11:33 PM
- - alan   Some topography o the limb visible in these http:...   Oct 2 2015, 06:07 PM
- - Herobrine   The weekly SOC release was about 90 minutes ago. 8...   Oct 2 2015, 07:00 PM
- - Nafnlaus   Tried stacking them to see if I could bring out an...   Oct 2 2015, 11:56 PM
- - alan   Quote from a recent NASA article QUOTE In these u...   Oct 3 2015, 09:16 PM
- - stevesliva   Those hazes are *blue* http://pluto.jhuapl.edu/New...   Oct 8 2015, 04:50 PM
|- - scalbers   QUOTE (stevesliva @ Oct 8 2015, 04:50 PM)...   Oct 8 2015, 11:10 PM
- - Nafnlaus   And how blue they are Such a simple image - the...   Oct 8 2015, 07:21 PM
- - ngunn   And it vindicates the wonderful coloured version o...   Oct 8 2015, 09:06 PM
|- - Ian R   QUOTE (ngunn @ Oct 8 2015, 10:06 PM) And ...   Oct 9 2015, 04:58 PM
- - Bjorn Jonsson   The blue color is interesting because it *may* mea...   Oct 8 2015, 11:09 PM
|- - Gennady Ionov   QUOTE (Bjorn Jonsson @ Oct 9 2015, 04:09 ...   Oct 9 2015, 08:46 PM
|- - fredk   QUOTE (Gennady Ionov @ Oct 9 2015, 09:46 ...   Oct 9 2015, 10:51 PM
- - remcook   Though note that that fractal particles, such as f...   Oct 9 2015, 08:05 AM
- - scalbers   Yes perhaps it should be bluer. I suppose we can s...   Oct 9 2015, 06:24 PM
- - Bjorn Jonsson   In hindsight this test render I posted 2 months ag...   Oct 9 2015, 07:45 PM
- - ngunn   I think you both (Ian and Bjorn) were absolutely s...   Oct 9 2015, 08:56 PM
- - Gennady Ionov   I can simulate what portion of pixel crescent is s...   Oct 10 2015, 12:32 AM
|- - fredk   QUOTE (Gennady Ionov @ Oct 10 2015, 01:32...   Oct 11 2015, 03:41 PM
|- - Gennady Ionov   QUOTE (fredk @ Oct 11 2015, 08:41 PM) It...   Oct 11 2015, 06:48 PM
|- - fredk   QUOTE (Gennady Ionov @ Oct 11 2015, 07:48...   Oct 11 2015, 08:46 PM
|- - Gennady Ionov   QUOTE (fredk @ Oct 12 2015, 01:46 AM) Do ...   Oct 12 2015, 06:38 AM
- - Gennady Ionov   If we multiply the green channel by 0.9, and blue ...   Oct 11 2015, 07:29 AM
- - scalbers   I thought it would be interesting to compare simul...   Oct 11 2015, 02:00 PM
- - scalbers   That's largely true though I'd be interest...   Oct 11 2015, 04:17 PM
|- - Gennady Ionov   QUOTE (scalbers @ Oct 11 2015, 09:17 PM) ...   Oct 11 2015, 06:51 PM
- - remcook   A tweet from the Pluto session at the DPS meeting:...   Nov 9 2015, 06:48 PM
- - alan   QUOTE Other results from the conference showed tha...   Nov 9 2015, 10:15 PM
- - scalbers   On an AGU poster I recall something like a .0045 o...   Dec 20 2015, 03:24 PM
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