Pluto System Speculation Options

[serpens]

Following up on Dobrovolskis' paper led me to a collection of papers from various authors, speculating on the Pluto-Charon binary system. It was compiled by Alan Stern and published by the University of Arizona in 1997, simply titled Pluto and Charon. While dated the papers remain relevant and make fascinating reading. Some extracts are in Google books. Well worth the search for anyone interested.

[Sherbert]

Remember, there are no catastrophic processes, only catastrophic events. Sometimes things just go SPLAT.

--Bill

Bill, you old rascal, excellent post.

[Bill Harris]

[JRehling]

Good idea that, maybe the subsurface "aquifer" of CO was penetrated by an impact and the pressure release, belched out a fluid slush of mainly CO. The breach would be sealed over with a "scab" of frozen CO. The raised, brighter, heart of the Tombaugh region comes to mind. An object about the size of the one that knocked out the dinosaurs, might do the trick.

I've inadvertently stolen this thinking in musings on the Pluto Near Flyby thread.

To develop it out a bit, there is a state of solid CO that packs a tremendous amount of physical energy when under pressure, and releases it explosively when the pressure is removed. The required pressure could only form very deep inside Pluto, but perhaps this condition was met. Then, a relaxation in the pressure could trigger a single, colossal explosion.

An impact might be the trigger. We also know that Pluto is venting stuff anyway, so maybe the integrity of the material that was providing the pressure crossed a threshold.

If any of this is true, one would expect it to happen, perhaps, only once in Pluto's history, so to have it happen very recently would be improbable, but not impossible.

[Bill Harris]

I don't think it's inadvertently stolen, but I do like your line of reasoning on the CO / CO2 energy release of the phase change.

There is a phase of solid carbon monoxide that stores a tremendous amount of energy and which can decompress explosively. While the pressures needed to attain this seem to be beyond the ability of Pluto's structure to create, except perhaps at extreme depth, I wonder if Tombaugh Regio might not be the one-time escape of a single explosion of CO from Pluto's mantle or core, going off like a fire extinguisher and blasting laterally (as well as into space).

On the other hand, it would be improbable for a one-time event to have happened so recently as the lack of craters implies, so perhaps its something somewhat less extreme but periodic that vents from Tombaugh Regio. Still, while a single event happening recently is improbable, it's not impossible. It would be nice to know the cratering rate in Pluto's neighborhood, to say the least.

Yes, rather like Coesite with an attitude--

Polycarbonyl
https://en.wikipedia.org/wiki/Polycarbonyl

--Bill

And add to this molecular gas ices and hydrocarbon ices and water clathrates all under alien conditions...

--Bill

[Sherbert]

I've inadvertently stolen this thinking in musings on the Pluto Near Flyby thread.

I'm just glad to see others are thinking similarly. I did not know about that phase change. As Bill says the other super volatiles are going to have their different influences. The Tombaugh region is mainly about CO, but the majority of Pluto is about Nitrogen and Methane. It is perhaps unfortunate that the NH close flyby is over this "aberration" on Pluto's surface. The images from North and East of Tombaugh will hopefully tell us more about pre impact Pluto, which one suspects is a lot more sedate.

The Cthulhu region near the impact area has steep cliffs, but away from there the sides of the basin appear a far more gentle slope. I'm thinking the depression is more an illusion created by mountainous terrain to the North and South of the equator. It may be at a similar level to the plains of the "temperate latitudes". Flows of Pluto's atmosphere travelling from "warm" to "cold" are going to travel to points where the vapour pressure and temperature conditions mean the gases, Nitrogen and Methane mainly, are going to freeze and collect. The axial tilt obviously messes with this simplified scenario, the predominant flow appears to be North to South. The "Ropey" mountains are in my eyes the Northern extent of the Southern mountains. This flow has definitely helped to spread Carbon Monoxide from the impact site, South, over the Sputnik Plain and on down towards the equator. Both aeolian transport and sublimation/deposition seem likely to be involved, modifying the initial overflow from the impact basin at the time of the impact, to create the current landscape.

[xflare]

I think the heart, at least the left side, is a vast cryovolcanic lava flow.

[Gladstoner]

I think the heart, at least the left side, is a vast cryovolcanic lava flow.

West Tombaugh Regio does appear more like a caldera with a lava lake than (what I think of as) a glacier.

[marsbug]

Looking at the images of the 'nitrogen glaciers', I'm reminded that the solubility of water ice in liquid nitrogen is unexpectedly high:

http://link.springer.com/chapter/10.1007/9...4613-9865-3_113

https://inis.iaea.org/search/search.aspx?orig_q=RN:16033601

given how ell these glaciers seem to flow, is a liquid component in microveins within the bulk ice a possibility I wonder, and has it been slowly eating its way into the water ice 'bedrock'? That would make the whole system a very interesting experiment into a large scale physical and chemical system the likes of which we simply could not do on earth.

[Rittmann]

Looking at the images I've come to some ideas that, so far, I have not seen from anyone. Since they are essentially speculative, I'll put them in this thread and not in the encounter thread.

1.- Equatorial dark band

Looking at the surface of Pluto and its crater distribution so far, I am under the impression that cratering is essentially on the equator. We can see in the maps that resurfacing has happened in the northern latituted, and Tombaugh region is very young, but the Cthulhu region has several craters, some of them filled with the dark element.

One of the first ideas that came to my mind was the possibility of a collapsed ring system around the equator. Before the encounter it had been commented that the Pluto system could feature a transient ring system created from dust from its moons. In the turbulent gravity environment of Pluto, with the barycenter far from the planet surface and Charon's pull affecting assymetrically the space around pluto, I speculate that instead of a ring system, dust would rain towards the planet's surface and collapse around the equator. Tidal locking with Charon would have affected the deposition over time, making two differentiate patterns. Craters would then have higher chances to happen around the equator if they were fragments of the original event that created the current system's configuration, and as time went by, would have rained down on Pluto's equator along the dark dust. Charon's influence would have prevented a slim ring to form, raining over a range of equatorial latitudes instead.

This idea has its own weak points. It doesn't explain Charon's dark pole - there should also be an equatorial belt in the moon -. It also doesn't explain why there appear to be dark materials on the peaks of some mountains.

In this scenario the original impact that created the double planet would have caused full resurfacing of Pluto and Charon, and over time Pluto would have received the rain of dust over its surface, along with some debris.

2.- Energy source for Pluto's current resurfacing

A global scale resurfacing event is likely to have happened in the event that created the Pluto / Charon system, if as it seems, it was created by an impact.

Pluto's mass is (1.305±0.007)×10^22 kg. It currently loses 500 metric tonnes of material every hour according to the data. Assuming a constant rate - which is a lot of assuming, since I believe Tombaugh is currently the biggest source for mass loss in the planet due to its young volatile exposed ices, in contrast with the older areas - we have the following numbers:

4.38*10^9 kg /year
1.971*10^19 kg in 4.5 billion years

We are three orders of magnitud below the whole planet's mass here, but this mass was originally only on the surface. Pluto's surface area is 1.77×10^7 km2, so on the current surface of Pluto could have lost over the life span of the Solar System 1.110 metric tonnes of mass per square meter.

Considering that the possibility for sub-surface liquid masses has been estimated in the scale of meters, makes me propose the following hypothesis: as surface mass is lost, underground liquid masses are able to expand due to the release of pressure. These masses could, in some places, crack causing faults - ices tend to be brittle - releasing on the surface as they expanded against the almost void of the surface of the planet.

In the areas where this first happened the process would speed up since the exposed clean ices from the underground lakes would sublimate at a higher pace than older, more stable surfaces. This would release faster enough pressure for even more underground deposits to burst into the surface, including water deposits.

According to this idea, Tombaugh region would have been the place where the liquid underground sources would have been nearest to the surface - it is more or less the exact anti-Charon area, so that could have influence through tidal heating in the past -. Once enough surface ices sublimated into the atmosphere and space, the pressure release would have caused the first nitrogen and CO underground sources to burst, flooding the surface and speeding up the process. As the process sped up, deeper sources with liquid water would have also bursted, causing the ice mountains to show up over the nitrogen and CO plains.

In the first hi-res image we can see several faults across older surface south of Tombaugh, but none of the faults seems to be affecting any mountain in the area.

Furthermore, this would explain the shorelines since the plains' surface would have sublimated over time, leaving the original terminators of the expansion process - still made of materials that don't as easily sublimate - to remain.

PD. My first post in this fantastic forum!

[ZLD]

Just to throw an idea out thats been rattling around in my head for the past week, with regard to the Tombaugh Regio area, I don't believe it is or was a an impact. Looking around the rim, there are areas that would allude to it being crater like but if there is tectonic activity, it could possibly form much of what is visible as well, more on this in a bit.

Let's back up a little. In 1989, Pluto was at perihelion and conditions were most favorable for the densest possible atmosphere from seasonal change. In the time since, the surface pressure appeared to be increasing until a rapid falloff observed by REX. During yesterday's science update, they didn't appear to have the data from the SOPHIA occulation observation. So we can't rule out the possibility that there could be error in the way atmospheric pressure is calculated during a distant occultation, or there could be an error in reading the REX data, or some other unforeseen error elsewhere. However, lets continue to assume everything is correct and accurate. This leaves the question as to why pressure would increase and suddenly fall off, especially with the abundant and constant release of nitrogen that is escaping.

Back to Tombaugh Regio. Blatantly, I feel the area is currently and has been a sea for a very long time, possibly composed of nitrogen. There well established areas that look like shorelines, theres what appears to be migration through the region, lack of any visible impact craters and very strange linear or polygonal features that overlay the region. During an earlier press briefing, an idea that this looked like a boiling liquid really piqued my interest.

A large assumption to suggest but if Pluto had a slightly denser than measured atmosphere during perihelion then this nitrogen sea may have been liquid at the surface, maybe even for just a few years. Then as Pluto began to cool off again, the atmosphere began to refreeze, decreasing pressure to a point where the nitrogen sea began to boil and eventually settled with a relatively thin membrane over the still liquid sea. As this action was occurring, it could have possibly thrown off atmospheric measurements as the nitrogen was boiling away and escaping into space. A large amount of nitrogen still escapes the body, possibly through the linear features in the region as well.

Back to tectonics. This is really out there but looking over the wonderful maps by scalbers, the area previously referred to as the 'train tracks' looks like it shares some similarities to Tombaugh Regio. I mentioned a while back from my versions of the stacked approach data, that it seemed like Cthulu possibly sat slightly above the mean terrain. I still personally see that in some regard with the higher resolution images. These dark areas may be a sort of continental plate and the bright areas like Tombaugh Regio more like a sea floor plate. The biggest contributor to this idea is the segment of the surface, running along the west side of TR. It appears very strikingly like a rift valley forming, and not simply ice burgs breaking away. If the previous maps of Pluto are at all accurate (they seem to be), then there is likely even more of the bright areas in the south that make up these sea plates. This further lends to why the dark regions would appear to be heavily bombarded relative to TR. As for the northern ice covered terrain, there appears to be a difference in types and maybe numbers of cratering between the areas just north of TR and just north of Cthulu. This could indicate that under this ice sheet is a continuation of these differing plates, softening craters over the less viscous areas.

[scalbers]

PD. My first post in this fantastic forum!

Welcome to the forum Rittman. I would like to check if your numbers come out better using the mass loss value I recall hearing, of 500 tons per hour?

[Rittmann]

Whoops! True. I've edited the post to match things. But this means that Pluto, assuming a constant loss rate from its birth - which is a lot of assuming - has lost 1/500th of its mass due to this process.

1.110 tonnes per square meter, if we use the density of N2 ice at Pluto's temperature as 1.35g/cm3, means a column of approximately 1500 meters per square meter. That is a lot!

My conjecture, though, is that the current escape rate is working at a far faster pace due to Tombaugh region's popping up having happened relatively in recent times - 100MY, for example -. Older, "baked" areas like the equatorial dark belt would have practically stopped sublimating elements since the dark material coating the terrain would act as some kind of protection - thus, the apparent surface is also older since this mechanism would have no power to resurface the area.

But if we account Tombaugh as the main area where sublimation is happening, and the event that bursted the current ices over its plains as 100MY old, then we can formulate a rough approximation:

1.- Tombaugh's exposed ices, even if it is a reduced region through Pluto, account for, let's say, 25% contribution to the overall mass loss.
2.- This increased rate has happened only during the last 100MY.
3.- I don't have the total surface area of Tombaugh regio. I will assume an approximate shape of a circle and an approximate diameter of 1200km. This gives a rough total area of 1.13*10^6 km2

So, 125 metric tonnes per hour from Tombaugh regio for 100MY gives:

1.- Mass loss: 1.095*10^17 kg during 100MY
2.- 97 metric tons per square meter of mass loss

This gives a total loss of approximately 77 meters of mass loss over the surface during 100 MY.

Considering that some think that the liquid layer for Pluto's characteristics may be just a few dozen meters below the surface, we may have here a plausible mechanism for the surface renewal. Add to this that the figures are all very rough, so a surface 200MY old would give 150 meters of mass loss, carving the shorelines we see. Or Tombaugh regio could account for far more mass loss than just 25% since it is not "baked", speeding up the process.

Why this area? If the wobbling we see by the moon tides on Earth is any reference, Tombaugh regio being anti Charon would be one of the highest original elevation areas in Pluto, or at least one that would have been the most active during the tidal locking with the moon, providing a source of energy over a long time during Pluto's history, and creating a concentration of pools near the surface.

All in all, here is my speculation for a mechanism for resurfacing of the planet.

[Bill Harris]

Not bad First Posts and welcome, Rittman. The Pluto-Charon system is an amazing world and with new (and improved) images arriving almost daily our knowledge of the system is evolving at that rate. These are wonderful times.

I am working up a "Poster Session" on the geomorphology of Pluto. This is, of course, presently a work-in-progress, and the initial Index image is at:

https://univ.smugmug.com/New-Horizons-Mission/PlutoCharon/

--Bill

[Bill Harris]

...Considering that some think that the liquid layer for Pluto's characteristics may be just a few dozen meters below the surface, we may have here a plausible mechanism for the surface renewal. Add to this that the figures are all very rough, so a surface 200MY old would give 150 meters of mass loss, carving the shorelines we see. Or Tombaugh regio could account for far more mass loss than just 25% since it is not "baked", speeding up the process...

Yes. And look at the phase diagrams for Nitrogen and Methane that I have seen posted here-- the triple point is attainable at reasonable temperatures and pressures. And that is not even considering the properties of admixtures of Nitrogen with other gases such as CH4, NH4, CO, CO2. Nor the properties of clathrates with the forms of water ice.

I am by no means a cryochemist/physicist so all this is mind-boggling to me.

--Bill

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