Pluto System Speculation Options

[Nafnlaus]

I was just going to say that those chunks of ice look like floating icebergs on some fluid but I was thinking it was a silly idea and maybe it is.

It's not silly at all - see my post above about eutectics. Especially if there's neon there (neon makes it almost too easy to have liquids at Pluto temperatures), but even if there's not. Examples:

* There's various mixtures of N2/CO/CH4/O2, without any neon, that have lower melting points than any of them have individually, including down to nearly 50K (Pluto is commonly said to get up to 55K)
* The temperature could easily get higher than the commonly cited temperature range for Pluto - that's based on very simplistic equilibrium-heating calculations. I'm sure the mission will give us far more accurate data on how hot Pluto actually gets - or at least, how hot it is right now.
* Local variations in temperature can occur in a body, for example, due to differences in albedo. Liquids could flow like "groundwater" from one area to another.
* There could be geothermal heating from within Pluto
* There could be heat from subduction of ices.
* There could be heat from transition between ice phases

And so forth. Beyond temperature, what's needed for liquids is pressure. Nitrogen needs about 18 meters of N2 ice (more if it's "fluffy" (probable) or mixed with other ices). Neon needs about 3x the pressure.

But the basic point is, if you hit the eutectic's triple point, even if the stuff originally fell as snow, it will melt on the bottom.

[Webscientist]

My first impression was that the bright heart (made of frozen CO and not CO2...) looked like a "banquise" or an ice pack.

The black patches along some limits of the polygons seem to be in line with my initial assumption according to which there is a layer of liquid hydrocarbons (methane, ethane...) beneath this bright uniform crust.

At what depth?...

Possibly the largest reservoir of liquid hydrocarbons is hiding beneath this intriguing area! Who knows?

That's my bet!

[dvandorn]

Kewl! Good to have a thread where we can speculate wildly. (ADMIN: With some restraint please. )

I'm wondering why the CO ice is all in Tombaugh Regio on the lit side of the planet. What would cause CO ice to gather just there? Altitude? Temperature? Is there a liquid CO "aquifer" underneath that only wells up here?

Remember that the area is getting the most insolation it will get during the northern summer. Yes, it gets more direct sunlight when the sun is high over the equator, but only for half a Plutonian day, so overall right now, even at a lower angle of incidence, it's getting insolation continuously. So it's not exactly a cold sink.

I think you have to start getting your head wrapped around the 248-year cycle of seasons on Pluto. It spends more than 50 years in each season, and more than a century of continuous insolation on each pole. Cold sinks are going to appear in odd places, build up ices, and sublimate back off as this cycle continues. And I'm thinking that each set of seasons are unique -- topography changes, ice deposition occurs in different places due to vagaries of wind and even weather -- so major ice depositions might occur in different places in different years.

Maybe the CO ice is a remnant of a major deposition that occurred in the best cold sink available on what was then the dark side when a big exposure of CO ice sublimated relatively quickly from the southern hemisphere? And the other ices deposited at the time have preferentially sublimated since the northern hemisphere began its summer, leaving only the harder-to-sublimate CO ice? If so, what around here sublimates more easily than CO ice? And maybe the pitted surface at the southern edge of Sputnik Planum is an example of where those other ices puffed out, leaving holes in the CO ice?

Also -- hitting the various things that have been crossing my mind -- if Pluto is losing 5 tons of nitrogen an hour to space, over four billion years that amounts to nearly 163 and half trillion tons of nitrogen, if that's been a relatively consistent loss rate. How many tons of Pluto is left? How much of the original body has been blown away? And how much more of other lighter elements might have been lost earlier in Pluto's history?

And, to answer my own question, a quick search shows me that Pluto has an estimated mass of 13 quintillion tons. A quick calculation tells me that the amount of nitrogen lost (again assuming a consistent loss rate) is 1.25e-5 percent of Pluto's current mass. So, I guess maybe not so much... sounds like a heck of a lot, though!

-the other Doug

[Sherbert]

I'm wondering why the CO ice is all in Tombaugh Regio on the lit side of the planet. What would cause CO ice to gather just there? Altitude? Temperature? Is there a liquid CO "aquifer" underneath that only wells up here?

Remember that the area is getting the most insolation it will get during the northern summer. Yes, it gets more direct sunlight when the sun is high over the equator, but only for half a Plutonian day, so overall right now, even at a lower angle of incidence, it's getting insolation continuously. So it's not exactly a cold sink.

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.

EDIT:- Strangely enough that was about a once in a hundred million year event, the rough boundary mentioned for the timeframe of the most recent activity on Pluto.

Looking at DLD's second, enhanced colour image, the distribution of material across the top of the icecap "land bridge" suggests a west to east flow to the equatorial winds here. It looks like material has been blown out of the dark Whale region up onto the icecap. It appears to be quite sharply bounded on the Northern edge, only small amounts of material have reached the areas of the pits and even less reaching further North to the Sputnik Plain. Prevented by the prevailing North to South atmospheric flow, presumably. There is not enough detail in the Colour map to try and spot turbulence at the boundaries of these gas flow patterns, reflected in the surface colouring. Might be something to look out for in the Hi Res images.

The coloured area, the cone of the ice cream, appears to be considerably lower than Sputnik Plain. The slope between them is seen mainly as the pitted terrain. The pits, almost certainly sublimation features, seem to form on slopes, in roughly parallel rows, created by the different insolation of the slope as shadows move up and down the slope. Similar rows of pits can be seen at the tip of Tombaugh, referred to by JB I think as "nests". I think they look like golf bunkers, except they are considerably larger.