Very illuminating paper that. The amount of exposed alpha N2 ice would seem to have an effect on the equilibrium of the whole atmosphere. Most interesting is that the two phases can exist as a mixture.

This suggests to me, Nitrogen frost build up to levels above a few metres results in a gradual phase transition, first to the denser, alpha ice allotrope and at even greater depths there is the possibility of liquid Nitrogen forming, perhaps in cracks and voids in the ice. A process similar to ice crystals building a glacier. This "liquid aquifer" might one would think, be trapped below the alpha phase Nitrogen ice, similar to oil and natural gas underground on Earth capped by an impervious rock layer, allowing pressure build up. All sorts of interesting possibilities arise if this is the case, especially if some heat is still emanating from the core below, or the "aquifer" is penetrated by an impact.

Bjorn posted a jaw-dropping animation in the Pluto Atmospheric Observations: NH Post-Encounter Phase, 1 Aug 2015- TBD thread. It's fast - blink and you'll miss it - but, well, holy cow is about the most coherent thing I can manage to say about it right now.

Well, thats the amazing thing, if Pluto's surface N2 is a solid solution, e.g. it changes from alpha to beta N2-ice and back again, raises some weird possibilities.
Phase transitions make great buffering solutions because of latent heat, literally "hidden heat".
That is, you can measure the temperature of the system with precision, but you won't know how much energy is stored in the system.
Or to paraphrase my old chemistry professor, "burn your fingerprints off pyrex test tubes look like normal pyrex test tubes"...

Point is, a feature that is N2 ice at, say 40 kelvin,
you won't know whether it's thin coat of frost on frigid H20 mountain,
or the last coat of frost on a N2 mud-pot geyster that is about to blow sky high.

The video below shows liquid Nitrogen freezes initially into an amorphous, "glass" like solid, before assuming the hexagonal Beta phase. There is a possibility, given the right temperature and pressure, of all three phases existing on the surface of Pluto should the postulated liquid Nitrogen from below, flow onto the surface in large volumes.

https://www.youtube.com/watch?v=c0rK2bLTimQ

The differing optical properties and grain sizes of crystals of Alpha and Beta N2 ice in a mixture are going to be relevant to its visible appearance. Phil suggested earlier grain sizes and transparency as a possible explanation for the appearance of the Northern Tombaugh "glaciers". Altitude of the terrain is important in determining the ratios of the two phases, which tends to suggest to me that this idea combined with "plastic" flow, possibly of amorphous ice, is along the right lines.

Another issue is sintering of surface ices and its effect on its physical and visual properties. On top of all that is contamination of the Nitrogen ice with other molecules.

More data definitely required.

Fascinating video, thank you for sharing it.

Not sure if this has been brought up already, but Krun looks much younger than Cthulhu. Krun displays few, if any, well-preserved craters at the current resolution. That said, there are lot of candidates for eroded craters.

This gives me more faith in the idea that the dark equatorial areas to a large extent simply are equatorial highlands (Krun, like Cthulhu, does appear to be elevated above Sputnik), possibly with different origins.

Related or not, here are some valleys cutting into Krun:



This (western) part of Krun also appears to have a rather rough texture, and appears very young.

It seems that the "Southern Outcrops" on Pluto are somewhat different than the "Northern Outcrops", although it might be that the Northern area is simply frostier. Krun seems to be old, eroded terrain, although southward it develops a "tiger stripe" exuded texture. With fuzzy images, it's too early to tell for certain.

And, oddly enough, Charon seems to have a similar N-S bedrock dichotomy with the added mystery of an equatorial rift zone.

What odd little worlds.

--Bill

The norther and southern hemispheres of Pluto and Charon may experience "seasons"
differently because of the interplay of orbital speed and axial tilt.

An article about 2 years ago had a good summary of the possible outcomes-

http://planetary.s3.amazonaws.com/assets/i...sons_apj-21.png

One possibility is that northern hemisphere retains a polar cap year round, e.g. "permafrost"
but the southern hemisphere doesn't develop an ice cap, and experiences "freeze thaw".

Here's the link to the article on Pluto and seasonal ice caps-

http://www.planetary.org/blogs/emily-lakda...w-horizons.html

Roughly speaking:
Southern hemisphere experiences a warm up from when Pluto is far away and moving slowly.
Northern hemisphere experiences a warm up when Pluto is close and moving quickly.

Hemispheres experience slow cool, quick warm, or vice versa.

Edit -
Ahh, never quite occurred to me, Pluto is like Asimov's "Nightfall"

North pole has a 60 year night, then has 40 years of perihelion twilight,
then a 60 year day, and 80 years of apehelion twilight.

Equator is even weirder, 60 years of twilight, 40 years at hot-equinox with 144 hour days,
then another 60 years of twilight, and 80 years at cold-equinox with 144 hour days.

From the activity timeline:


What is this being used to determine?

I don't know. REX is a passive device assoc with the main antenna and is designed for atmospheric studies., Possibly it's doing high altitude/atmospheric depth studies as the spacecraft is conducting normal comms?

That activity timeline blurb almost makes it seem to be acting like radar with reflected signals. At least I presume that the main beam is so well-collimated that there will be little scatter to Pluto to reflect with normal Earth-comms.

--Bill

IIRC, REX can be active, so the receiver may be on earth.

Great description of the situation, thanks! Let's hope there are no 'intelligent' inhabitants to find a problem with the lighting arrangements.

It calculates a series of animations about the New Horizons flyby:
1. Like the LORRI imaging (+motion blur): https://youtu.be/N9LTFsSulUw
2. Color motion blur: http://youtu.be/XSHlcw0ead4
3. Color motion blur, large scaling: https://youtu.be/VXJqTAVeAgs
4. Color, fast: https://youtu.be/rUiH8tq2zjc

You can download source files from ftp://gionov:NG@46.45.15.20/Movie/

As example a frame just after solar eclipse:

Gennady, those movies are AMAZING! Utterly breathtaking.