Agreed.

I guess I'm just not conveying the basic idea here. It is much easier to sample earth's atmospheric CO2 levels by using a weather balloon, compared to going to greenland and taking an ice core.
But data from a layered deposit like the greenland ice core, gives you multiple data points, which is orders of magnitude more useful than a single data point. Actually, it literally gives you dimensions; a single data point is one-dimensional, access to multiple data points that stretch through time allows you to derive multi-dimensional analysis.

If sputnik planum does experience convection, then that raises the possibility of layered deposits recording millions of years of flux of meteoroids and meteoric dust, as well as the flux of icy particles which quite simply can't exist inside the current snowline.

Pluto has a N2 atmosphere, it gets hit by cosmic rays, and by solar UV.
That means cosmic rays should create both carbon 14 and beryllium 10
while UV creates tholins which can precipitate them down to the surface.
That raises the possibility of useful radiologic dating over the range of both thousands of years using C14, and millions of years using Be10.

That is why sputnik is potentially the most important sample site in the solar system.

So, we may have "Mare Sputnik"

Recent conferences suggest that Sputnik Planum is 3-4 KM of N2! http://www.planetary.org/blogs/emily-lakda...s-from-agu.html
"that argues for a layer of nitrogen ice within Sputnik that is about 3 or 4 kilometers thick; it's thicker at the middle (where cells are larger) than at the edges." So, 3-4 km of N2 on Pluto, is the same as 3-4 km of H20 in Earth's oceans.

But, if the N2 is 3-4 km deep, if you go deep enough, would it still be ice?


So, figure Pluto surface is around 40k, (currently) then the depths of Sputnik could be 60k to 120k warmer than the surface.
And it looks like 63K is warm enough to create liquid N2.


So, eh, Pluto gets up to 63K, the triple point for N2 and CO.
On Earth, a polar ocean exists at 0 Farhenheight, the freeze-thaw point of salt water.

Very interesting, perhaps Sputnik thaws into a sea, like the lakes of Titan?

This excerpt from Emily's Planetary.org post is pretty handy as it summarizes information that is useful in making sense of various Plutonian processes:


Most interesting to me are the relative densities and miscibility of the various ices.

Some thoughts and considerations (already stated by others, or guesses on my part -- right or wrong)....


Water ice is basically the 'rocky crust' of Pluto. It can intermingle with and be altered by the more volatile materials, just as granite, basalt, limestone, etc. can be altered by water in a number of ways (dissolved, dispersed as clasts, etc.).


The mixing of one ice into another can alter their properties in a number of ways (e.g. sublimation points). I'm reminded of the properties of a cooling body of magma, but.... different (i.e. sublimation could take on a role like crystal differentiation, but 'in reverse'). And then there is the question of these properties at various depth pressures.... An igneous petrology textbook may still be handy here....


This could apply to diapirs and 'magmatic' bodies as well as glacial ice. Plus, how high can a pile of each ice type (or mixtures of the two) be before it flows under its own weight?


Methane here reminds me of silica/quartz in a terrestrial magmatic system, but with a lower melting (sublimation) point. Would that make water ice the 'feldspar'?


In a sense, tholins may 'play the role' of dust on Mars. Since tholins are a refractory residue, it could be spread across the planet via the atmosphere, and accumulate in certain spots in various ways for a number of reasons.

Again, this could be mostly (or all) wrong. I'm just trying to grasp for any kind of familiarity here. At least there are impact craters to provide some context.

Sputnik Planum cannot melt into a "sea" because Pluto's atmospheric pressure is far too low to support the liquid phase of N2:

Phase diagram is from a recent (~2014) paper " The surface compositions of Pluto and Charon"
http://www.boulder.swri.edu/~buie/biblio/pub095.pdf

Article doesn't specify pressure, they are dealing with the surface of Pluto, I'd be surprised if they forgot about pressure!
So, N2 on pluto is kinda like H2O on earth, you never find it pure, it usually has something dissolved in it.

But, let's assume surface N2 (actually a mixture) must be solid, or gas.
That means any transient bodies of liquid N2 would "ice over"
not because of cold temperature, but because of lowpressure. Weird eh?

I believe they were talking about subsurface liquid nitrogen where temperatures and pressures are higher.

Perhaps, except the paper is about infrared spectroscopy.
Since they're talking about telescope observations of the spectra Pluto,
I figure they know enough to look at figures for the surface of Pluto...

Interesting idea. You need about .1 bar of atmosphere to allow N2 to flow like a liquid on pluto.
Basically, if Pluto had a transient warming event, either procession or perhaps a collision,
the surface temperature would rise to 63 Kelvin, then you'd start melting N2 into atmosphere,
and once you have .1 bar of N2, you could get liquid.

A recent paper calculated that noted the the 10 microbar atmosphere of Pluto would freeze or condense
out into a layer under 1 millimeter thick across Pluto.
Recent numbers suggest Sputnik is about 3 Km deep and appears to be filled with N2 ice.
Some back of the envelope calculations suggest that the amount of N2 ice in Sputnik is just about
the same as the amount of N2 for a thick transient atmosphere where N2 could flow.

Say, current atmosphere now is 10 millionths of a bar, to allow liquid N2 you need .1 bar or 100,000 millionths.
So, you need about 10,000 times more N2.
Based on the 1 millimeter ice gives 10 bar atmosphere, you'd need roughly 10,000 millimeters,
or about 10 meters of N2 ice across pluto vaporized to create a .1 bar atmosphere.

Ok, sputnik appears to be 3,000 meters of N2 ice in one place. Quick size estimate, take 3 great circles
and you get 8 quadrants for a globe, each quadrant is three 90 degree angles draped on the globe.
So, roughly, about 10 sputnik sized areas to cover each quadrant- think of it like stacking balls,
inside the triangular area, bottom row of 4, next row 3, next row 2, top row 1.

And oddly, images of pluto divide pluto into six 60' longitude lines, not 90s, but you get the idea



So, a quadrant is 1/8 or 12.5%, of the surace, at about 10% of a quadrant sputnik covers roughly 1.25% of Pluto.
Call it 1% to keep the math easy. Then 3,000 meters of ice divided into 100 pieces would each be 30 meters thick.

Rather interesting actually - if Pluto does have the occasional runaway green house, (or impact)
it might get to 63 Kelvin with a transient one-tenth bar atmosphere and have liquid N2 for a while.

And it seems like the volume of ice in sputnik is just about what you would see if that entire transient
atmosphere froze out into one polar deposit.

A couple thoughts about liquid nitrogen in/on Sputnik....

As we all have seen, water ice is less dense than liquid H2O, so it floats on the surface. I'm not sure if I'm able to work out all the thermodynamics at this point, but I believe the surface ice serves to insulate the liquid body beneath it. This is why fish can continue to live beneath ponds and lakes in some of the coldest climates.

Solid nitrogen, on the other hand, is denser than its liquid (I'm pretty sure about this). Any N2 ice that forms at the surface would tend to sink to the bottom. As heat convects upward and radiates into space, the whole mass should freeze and remain that way. However, if more liquid is being drawn from another source, or if an internal heat source is melting the deeper nitrogen (as both could be the case with a magma chamber beneath a volcano), then all bets are off.

Question:

Would water ice, as it would exist at the surface and at depth on Pluto, be soluble in liquids (N2, CO, and/or CH4) that could potentially be present in the subsurface? If so, that could go a long way in helping explain some observed surface features.

Well, vice versa for clathrates.
There are some conference papers that consider internal structures with a clathrate layer (N2 or CO or CH4, encased in a soccerball of H2O) along with silicates, interior oceans and ices.

Would that also be the case under various other conditions? As it turns out, water ice apparently can dissolve in liquid nitrogen, but can be done only on a small scale under difficult conditions in the laboratory. Imagine how complex the interactions are in the vast scale and intricacies of Pluto's crust and mantle, not to mention all the unknowns (and unknowables). It may be centuries before we have a solid grasp of what makes Pluto tick.

Liquid nitrogen is a lousy solvent. Especially for polar materials like water ice.

IDK about dissolution of clathrates. Clathrates are extended cage structures of water ice (or other molecules) surrounding a caged molecule in a capped off host-guest interaction. Unclear if one can "dissolve" an intact clathrate. True dissolution would need to break up clathrate structure.

What is largest clathrated structure that could be intimately dissolved by liquid nitrogen?
What is smallest clathrate structure that could still be considered a structurally stable clathrate?

Thank you. That would put constraints on possible processes.

Would mixing in carbon monoxide with the nitrogen affect the solubility of water?

Probably.

Actually, in real life, all the volatile ices are mixtures, N2 and CH4 and CO all appear to be miscible in each other.

Carbon monoxide, CO, is an interesting suggestion for modifying H2O solubility.
Both are polar, and both contain oxygen, so the molecules are at least somewhat comparable in size.

So, while oil and water don't mix, adding soap allows them to.
Similarly, N2 and water might not mix well, (still not sure about measurements at Pluto temp & pressure)
but adding carbon monoxide might allow more miscibility.

Thanks for the link. Interesting stuff.

A few more questions to add to the pile....

- Couldn't sublimation of nitrogen (et al.) at the surface also erase features such as craters?
- If so, would it occur so slowly that its effects would be superceded by other processes (i.e. one or more of the three mentioned in the article)?
- If the sublimation did occur fairly rapidly, how then could the age of the surface be determined.... or even defined?
- Could meteor impacts influence the arrangement of the (eventual) patterns of the surface pits? If so, older impacts potentially could be identified.

Come to think of it.... It is fascinating to think about the effects of impacts into nitrogen ice. I'm not sure that I can accurately imagine such a thing....

That has occurred to me, too. A clathrate couldn't dissolve and still be a clathrate. But could it weather (physically break down) into a minimum clathrate "cell" or structure? I tend to think of clathrates as being akin to silicates at these temperatures, but that is not a strict analogy since the SiO4 and H2O bonds are way different. What would clathrate nanoparticles behave like?

'Tis truly an alien world.

--Bill

The nut-cluster'-like texture of the rolling hills around Wright Mons is interesting, particularly in the lower left:

Click to view attachment

This knobby texture appears to be present in various forms in many other areas on Pluto, including in the ancient terrain of Krun Macula (center of image):

Click to view attachment

And in the linear, fingerprint-like texture in areas north of Sputnik:

Click to view attachment

And the Zebra herd mountains:

Click to view attachment

Joint patterns in the water-ice crust come to mind, but it may be more to it than that.

FWIW, it could indicate that Wright Mons itself is made up of water ice.

I've been examining satellite imagery of the Arctic/Antarctic and Greenland. This is probably the closest Terrestrial analogy to Sputnik Planum we have. And going further afield from strict analogy, I've also looked at the ice-sheets/lava fields of Iceland for ideas away from the Tombaugh region.

There is some work on ice clathrates of methane CH4 and ethane C2H8 forming at geologic depths on Titan.
http://spaceref.com/saturn/icy-aquifers-on...e-rainfall.html

The inference from Titan is that in the icy bodies of the outer solar system, clathrates could form a thick subterranean layer.



At these temperatures, really over-simplifying

water ice = basaltic ocean crust
volatile ices = oceans
clathrates = continental crust

The study about Titan and clathrates notes that clathrates are good at separating liquids with different sized molecules.
For Pluto at depth, where you might have liquid methane, liquid N2 and liquid CO, that separation effect could be very interesting.
Methane clathrates would be similar on Titan and Pluto, and although carbon monoxide and nitrogen are chemically different from ethane,
the molecules are roughly the same size as ethane, so the cage-size based fractionation should be very similar.

So, Plutonian crustal clathrates might show the fractionation effect mentioned for Titan, e.g. they might be able to separate liquid phases
because of the smaller size of the CH4 molecules compared to the larger CO and N2 molecules.
One result of this could be that some areas on Pluto are underlain by deep methane aquifers while other areas are underlain by aquifers of carbon monoxide and nitrogen.

On Titan, the clathrates not only separate chemicals but appear to polymerize then, methane to ethane, ethane to propane.
So, perhaps at depth, Pluto clathrates could catalyze methane, ethane, propane; and also carbon monoxide to polycarbonyl.

Finally, if clathrates can catalyze polymerization of three CH4 molecules into propane,
then perhaps starting with CH4, N2, and CO results in polymerization into red tholins?

There's a bit of discussion about clathrates, CH4, N2 etc, in regards to Enceladus.

http://www.unmannedspaceflight.com/index.p...ost&p=77810
A Clathrate Reservoir Hypothesis for Enceladus' South Polar Plume
Susan W. Kieffer, Xinli Lu, Craig M. Bethke, John R. Spencer, Stephen Marshak, and Alexandra Navrotsky
Science 314, 1764-1766 (2006)
Abstract
Supporting Online Material

See also the accompanying News of the Week article "A Dry View of Enceladus Puts a Damper on Chances for Life There" by Richard Kerr.

So clathrates can be considered to be the zeolites of an icy world. Strangerer and strangerer...

--Bill

Well, not quite. It's not about large void spaces like zeolites,
rather it's the incorporation of a "volatile" into the solid crystal structure of the "rock".

On early earth, the first rocks to cool would be basalt.
Basalt is the dense black rock that makes the ocean crust.
When you re-melt basalt in the presence with water, (e.g. run basalt through a subduction zone)
the water is incorporated into the mix and you get granite, the less-dense light colored rock that
makes the continental crust.

So, on outer planets, "pure" H2O ices would be analogous to "basalt",
while the H2O clathrates would be analogous to granites as rock that has incorporated a volatile into
the crystal structure.

That is an excellent analogy. I tend to look at terrestrial clathrates, with the methane clathrate or methane hydrate being a type example, as a magical, mystical substance that binds up methane and therefore is akin to a zeolite. The classical description is a "cage structure enclosing methane molecules" and so on. Fairly simplistic.

I need to go do some reading...

--Bill

Early Lunar studies suggested that "conical" craters are the product of either volcanic (or gas) vents or of the sapping (or draining) of fine dust into a subsurface cavity. Given that these craters occur on a water-rocky terrain on could speculate that they are gas vents.

--Bill

Excellent and captivating presentation (at Drexel University) by Alan Stern that I've just followed on youtube:

https://www.youtube.com/watch?v=mIfqjbCNO3s

Regarding the famous "snakeskin" terrain, he says the composition involves methane ice. The pseudo-stalagmites may be composed of methane ice...

He says there are sinuous channels which may be related to ancien flows of liquid nitrogen at a time when the atmosphere was heavier, denser.

He postulates the presumed convection process associated with the polygons of Sputnik Planum may be related to an internal heat source from the progressive freezing of a water ocean beneath the icy crust. The heat is expelled upward from the freezing process... That's at least his favorite assumption at the moment.

Bump.

Wow. Flowing liquid nitrogen may have carved drainage channels Pluto?


https://www.youtube.com/watch?v=mIfqjbCNO3s
One hour, two minutes in.

Noticed that a stitched black & white lorri image by wildespace shows the area with the channels
http://www.unmannedspaceflight.com/index.p...st&p=227627

What wonderful worlds. Even though the temperature is low they ar not stuck in a deep-freeze.

--Bill

Bump- So Pluto is like the "Diamond Mountains of Lower Pomerania" That's the Brothers Grimm fairy tale, where a finch sharpening it's beak wears down a mountain. Instead, every 800,000 years, Pluto warms, a thin atmosphere forms which allows brooks and rivers of N2 flow for a few years. Then back to endless winter to wait almost a million years...

http://phenomena.nationalgeographic.com/20...-lake-on-pluto/

I recall that there have been findings that Mars has had extreme periods of tilt in its past, because of the lack of large satellites to prevent a wobble, but how would Pluto's axis undergo precession in such an extreme way, though? Doesn't Charon stabilize the axis just like our Moon does for Earth? Certainly intriguing...

What would be relevant are the moment of inertia of the system and the torque that is applied to the system. We can't know the internal moments of inertia of Pluto and Charon, but I would guess that the system's MOI can be estimated from externally observable quantities. There should be an answer for this, but it's a research project to get to the bottom of it.

Pluto's orbit is tightly controlled by Neptune, which says something about how much Neptune influences the Pluto-Charon system. But the answer to your question involves pages of math.

Eh, as to Mars, there was a recent paper and discussion that the weight
of the Tharsis bulge actually shifted the martian equator by 20 degrees.
Basically, Martian valleys/tropical rain bands and ice fields only make sense
if you turn Mars by 20 degrees, then the highlands and lowlands are balanced.

Pluto should be susceptible to the same crust-shifting effect, ice re-deposition
causes a huge mass redistribution, which forces the outer crust to shift.
Neat thing is, on Pluto, every 800,000 years, that ice could melt or sublimate,
and then re-deposit somewhere else, causing ANOTHER round of crust shifting.

Interesting to think of that interationc between atmosphere and planet.
On Venus, it's possible that the atmosphere has actually reversed the rotation of the planet,
on Pluto, it's possible that the weight of the frozen atmosphere reorients the poles every few million years.

No surprise there

Thanks for the info from you both, though still odd to consider. A Plutonian equivalent of the Milankovitch cycles? The Sun is too distant to have an effect, so it must be either Neptune or internal forces. Long term observations will shed light (no pun intended)...

Given the fact that Pluto and Charon are tidal locked and the mass ration is 0.117 the axial tilt of Pluto should be absolutely stable. Pluto's large axial tilt is almost certainly the result of the collision that formed Charon and most of the features we see could be attributed to compressive and despinning stresses and tidal bulge collapse. There would have been significant tidal stresses and associate heat energy generated as Charon receded. To put it in context, Just imagine the tidal stresses and ocean tides on Earth as the moon slowly receded from just outside the Roche limit to get an idea of what occurred on Pluto. The thing is that we really do not have a clue when the Charon forming collision occurred and the final gravitational lock could have taken place not so long ago.

It is hard to justify any correlation to Mars.

The Sun and Moon exert a torque on the Earth that causes it to precess with a period of 26,000 years. The same happens, at a slower rate, with the Pluto-Charon system relative to its orbit. The plane of Pluto's orbit around the Sun also regresses relative to the orbits of the other planets.

Details here, with lots of math: Dynamics of the Pluto-Charon binary

Thanks for the link alan, 3 million vs 26,000 year cycles, Earth's axis is practically chaotic by comparison.
I'm starting to warm up to this theory of a thicker prehistoric atmosphere (no pun intended); not bad for a nearly 20 year old book!

Hypothesis was come upon when I saw the first images of Enceladus, could see three obvious strikes, developed an idea of what I thought the rest of the surface of the moon would look like, ended up being 95% right about five strike impact being explanation
for plumes and most surface features. Tried to tell Dr. Porco on CICLOPS in 2005 what I saw but she had already disagreed with another person who suggested he saw an impact in the images. When I first saw "heart-shaped" feature on Pluto I could see an obvious
large, very geologically young impact crater at Sputnik Planum, with many secondary effects that explain almost all previous, current, and future observations of New Horizons at Pluto. In the young geology map of Sputnik Planum released two weeks
after I stated this on Google+ and Twitter, think I can see four impacts coming from southerly direction with impactor rotating clockwise as it strikes. Tartartus Dorsa is the material thrown up by the impact refreezing onto the surface of Pluto afterwards.
This explains the pattern on the surface, the unusual composition, and its very presence. Piri Planitia and other such features are secondary impacts. Convection did occur after impact pushing the old surface (the Montes) toward the edges of the spherical
impact site with the ice volcanos and glacial activity side effects of the heating and cooling of the surface material. Have been reading this site for ten years but this is my first attempted post. Am working on more detailed, coherent explanation with pictures.


Kenneth G. Tompkins