[X] My Assistant

[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]

And, as usual, when playing with numbers, I got one wrong. Somehow I thought I had just read Pluto loses 5 tons of nitrogen an hour. I find I left off a couple of zeroes, it's 500 tons an hour.

So, I believe that makes the amount of nitrogen lost closer to 16.33 quadrillion tons over four billion years, and that's more like (if I'm figuring the scientific notation right, that was always hard for me to think in) 1.25e-3 percent of Pluto's present mass. More, but still a pretty small percentage. Nothing like the half of a percent that was estimated as little as ten years ago by those who anticipated a lot of gas loss from our favorite little KBO.

-the other Doug