[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]

Also, I've not seen this mentioned specifically, perhaps the weight of the equatorial ice cap that is Tombaugh Regio is compressing the underlying water ice crust and causing the tectonic cracking we see around the region. Specifically, I'm thinking this could be the mechanism that created the radial cracks coming away from the region and extending into the Cthulu region.

That would make as much or more sense to me as the radial cracking being caused by an impact. Other basin-like impacts into icy worlds, like Callisto, for example, generate cracking in concentric rings around the impact point. These are cracks extending outward radially from the center of what appears to be a gigantic pile of nitrogen ice covered by a layer of CO ice. The weight of that pile could be what's deforming the surrounding terrain and causing the radial cracking.

-the other Doug