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Pluto Surface Observations 1: NH Post-Encounter Phase, 1 Aug 2015- 10 Oct 2015
nprev
post Aug 1 2015, 05:53 PM
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This topic will contain images & discussion of same as they arrive during the extended download period. Similar threads will be opened in coming months as required as acquired data & discussion proceeds.


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Gennady Ionov
post Aug 2 2015, 07:54 AM
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User torque_xtr (http://www.astronomy.ru/forum/index.php?action=profile;u=28931) proposed the idea that Sputnik Planum is basin filled from the atmosphere by nitrogen. In this regard, I simulate the amount of heat obtaned by Pluto from sun irradiation.
For a start I make the map, in which replaced the central part of unexplored region near the south pole into Sputnik Planum vicinity, so you can see how much energy is absorbed bright and dark areas near the south pole.
Figure shows amount of energy absorbed by surface of Pluto in one turn around the Sun.
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Colour picture shows the solar irradiation in the projection relative to the rotation axis of Pluto.
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Next pictures was made in projection relative the axis perpendicular both to the rotation axis and direction of Charon:
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At the center of second projection is a south pole, the north pole is on the left and right edge of the picture, the upper and lower edge are equatorial points with longitude 90° and 270°.
Due to the large inclination of the rotation axis of Pluto to the orbital plane, Pluto's polar regions on average much hotter then equatorial region, so that in contrast to the Earth and Mars "polar cap" have to look at the equator. Minimum insolation during the plutonian year gives 1.703 gigajoules per square meter, the maximum - gives 1.952 GJ/m^2.
Area Tombaugh absorbs a minimal amount of solar energy over the entire all surface of the planet. If it is assumed that the emissivity in the far infrared range varies less than in the optical range, Sputnik Planum would be cooler in which there is a continuous deposition of gases from the atmosphere occure. And this process is the driven force for glacier flow.
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Gennady Ionov
post Aug 2 2015, 05:58 PM
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Excuse me, is there somewhere information about exposures of LORRI and MVIC images of Pluto from the night side? It will be seen night side of Pluto surface in Charonshine?
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scalbers
post Aug 2 2015, 06:19 PM
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There are images (yet to be downlinked) of Pluto lit by Charon, and the central area lit would be near latitude 0 / longitude 0

Interesting to note minimum insolation at the equator over the course of a Plutonian year. Does the tilt of Pluto's axis vary over geological time scales? I'm wondering why the deepest blue in your upper Pluto color image (area of minimum absorbed solar radiation) seems longitudinally offset from Tombaugh Regio?


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Gennady Ionov
post Aug 3 2015, 08:24 AM
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Color pictures give density of irradiated solar energy, not absorbed solar radiation. Density of absorbed energy are shown in black-and-white pictures (it is simple multiplication of irradiated density by (1-albedo)). The variation of color along the equator has a numerical nature, and the real variation due to solar eclipses significantly less.
Next picture shows eclipse term.
Attached Image

Source of variation in previous version of pictures was non-constant time step of integration (the algorithm decrease time step during solar eclipse by Charon) and fractional turns of Pluto around it axis in one orbital period.
Now these shortcomings are eliminated.
The radiation can be considered constant along the equator, and the formation of the Tombaugh Regio can be explained by large impact feature, which was the seed for the condensation of gas (due to opened lighter surface). The presence of the "equatorial cap", together with the formation of impact has led to a redistribution of the masses, so that the pendulum has swung Pluto along the line passing through the center of the masses of Pluto and Charon.
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Habukaz
post Aug 3 2015, 10:14 AM
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In Pluto's north, there are these dark smudges (native res and enlarged) that I wonder if could be geysers or geyser remnants:


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Further north (I think..) is another smudge (and an apparent linear feature next to it, thrown in for good measure):

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(between them sits this obvious smudge feature, but it looks somewhat unrelated)

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One can find other similar features in the area.

Further south, we do of course also have all these smudges in Burney crater:

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One of them clearly looks like it has a tail:

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Then there are those other numerous things with dark centres and bright haloes

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they look like craters, but their distribution is a bit odd (there are what looks like a bit like tail features (streaks) in picture above, also). Most of them look relatively spherical, but some might be more irregular in shape:

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There are also these really messy areas (not far from the previous feature) that could be related:

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For comparison, here are some dark smudges in the geyser region of Triton:

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Bill Harris
post Aug 3 2015, 02:11 PM
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QUOTE
Interesting to note minimum insolation at the equator over the course of a Plutonian year.

Yes.
...

--Bill


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Gennady Ionov
post Aug 3 2015, 02:30 PM
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Another interesting feature of relief: small dimples. I suppose that it is an analogue of the dunes in the desert, caused not by the wind but solar irradiation conditions.
Oriented to the Sun the north side evaporates and on the shady south sides condensation occurs. Thus, the instability of a flat surface develops and slowly creeping dunes to the south (when in the northern hemisphere is summer). Therefore, the perpendicular meridians orientation of formations can be observed.
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scalbers
post Aug 3 2015, 04:34 PM
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QUOTE (Bill Harris @ Aug 3 2015, 02:11 PM) *
The insolation at any point will be the product of the solar intensity (x) a function of the solar elevation (x) a factor of the Sun's time above the horizon (x) whatever I've not thought of. I suspect that we'd need some sort of Calculus to describe that, with sine/cosine wheels to vary things.

Dang. What a can o'worms. Much easier to crank out purty pictures, but less fun. smile.gif

Maybe an additional assumption of a circular orbit would help provide a useful analytical expression to help picture this?


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JRehling
post Aug 3 2015, 06:44 PM
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I expect Pluto's axis of rotation to be very stable because of the gyroscopic effect of Charon in the Pluto-Charon system. Also, the resonant orbital behavior with respect to Neptune should be stable.

Note that Europa has an icy crust which is decoupled from its interior and rotates very slowly, at a rate that has not been established, with respect to Europa's interior. I don't know if that possibility exists for Pluto or Charon.
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Bill Harris
post Aug 3 2015, 07:48 PM
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QUOTE
an additional assumption of a circular orbit would help provide a useful analytical expression

That would help and could easily be added in later.

QUOTE
Europa has an icy crust which is decoupled from its interior... don't know if that possibility exists for Pluto or Charon

Possible. Without a significant interior heat source to actually melt an icy mantle, at-depth and away from STP (Std Temp Press), the various ices (water plus whatever else) and gases could make a high-viscosity flow which could decouple crust+mantle over geological time frames. At first look Pluto's surface looks smooth and flexy and may well be mobile at-depth, but Charon, with the Mordor region crater and the equatorial Chasmas would seem to be cold, frozen and solid.

IMO.

--Bill


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ngunn
post Aug 4 2015, 12:13 AM
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I don't think the surface is decoupled from the interior here, though I'd like to be wrong.
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Bill Harris
post Aug 4 2015, 01:00 AM
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There is no evidence either way, but I don't think so either. 'Tis a possibility.


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lollipop
post Aug 4 2015, 10:02 AM
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"Pluto’s insolation history: Latitudinal variations and effects on atmospheric pressure" by Earle and Binzel in April's edition of Icarus is probably the last word on Pluto's insolation history. They've done all the calculus so we don't have to!
For those without access there are various papers on Arxiv which touch on the subject.
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Bill Harris
post Aug 4 2015, 01:36 PM
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Yes! I'm planning to read that once I get into town to the Library.

It is the last word as of April, but I'm sure that there will be many other words post-encounter.

--Bill


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