The Frozen Plains of Pluto's 'Heart'

New Horizons has sent back new images of Pluto, including a close-up view of the "Tombaugh Regio," which resembles a giant, pale heart stretching 1,600 km across the dwarf planet's surface. The new images show a broad plain free of any craters, broken into irregular segments by shallow troughs. Scientists don't know how they formed, but here are two leading theories: "The irregular shapes may be the result of the contraction of surface materials, similar to what happens when mud dries. Alternatively, they may be a product of convection, similar to wax rising in a lava lamp." This image comes alongside new data on Pluto's extended atmosphere.

NASA has released other new findings from the Pluto region, as well. Pluto is trailed by a region of cold, ionized gas ripped away from its atmosphere by the solar wind. We've also gotten a close look at Charon, Pluto's biggest moon. One unusual feature is a sizable mountain rising from an even larger depression in the moon's surface. On top of that, NASA has released the first look at Nix, a tiny satellite of Pluto roughly 40 km in diameter. The image is highly pixelated, but we should get a better image tomorrow, during New Horizon's Saturday downlink. The NY Times has a gallery of images, which also includes pictures of Hydra (another small moon) and a different shot of the Pluto's plains area.

Comments

Re:Heart Oblique Impact?

[Rei]

It seems more complicated than that (even ignoring that impacts don't generally make heart shapes). For example, have you seen the carbon monoxide data? It's all clustered in that area. Why would an asteroid make carbon monoxide cluster there?

There's some really interesting things going on. Take a look at this picture and think of what it looks like to you:

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Doesn't it look like... well... a shoreline?

Now take a look at those fractures in Sputnik Planum - notice how they have a curious inner ridge:

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Where else have we seen that before? Oh right, Europa:

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It's the shape of a liquid welling up through a crack and freezing due to a drop in pressure.

To me, this shows all the signs of a cryosea underneath an ice cap. Which leads to the question: can that occur on Pluto? And the answer is, "probably". With N2, CO, and CH4, you can get eutectics with triple points as low as 51K (a naive solar equilibrium-temperature calculation for pluto's surface, without any other sources of heat, reaches up to 55K). Add neon into the mix and it gets down to 24,6K. The key is, these liquids can't exist on the surface - they require pressure to exist. Which means that they can only exist as aquifers and subglacial lakes/seas. Pure nitrogen requires about 18 meters of pure nitrogen ice (more because it'd have pore space and be mixed with lower density ices). Pure neon would require about 3x as much.

The flat areas in Tombaugh Regio have two radically different appearances. One is the aforementioned area that looks like sea ice with frozen cracks (Sputnik Planum). The other is what's being called a "pitted" terrain. The latter touches the "shore" of the regio, while the former is deep in the middle (at least, from the pictures revealed so far). If one wanted to step even further out onto the limb here, they could posit that the "pitted" terrain involves these ices sitting directly on "bedrock" (which in a pluto context here is water ice), while the terrain that looks like sea ice would have liquid dozens of meters or more down.

But this is all just along one line of thinking. There's just so many possibilities right now. One notices, for example, similarities with various pluto features and frost-heaving earth features like pingos and ice wedges. But it could be something completely new entirely. This isn't water we're dealing with.

A real crazy thing is to think about how there might be vertitable explosive processes on Pluto. Solid nitrogen that forms due to decompression undergoes an energetic glass to crystalline transition. And overall does really weird stuff when freezing (start about a minute in).

Also note that there is nitrogen being lost from Pluto. Lots - 500 tonnes an hour. Over geological timeperiods, that's a massive, massive amount. Pluto loses its atmosphere 2 1/2 orders of magnitude faster than Mars. And yet it's still there. So where's it coming from? The team already pointed out that there doesn't seem to be a planetwide layer of deep nitrogen ice. To me that only seems to leave the possibility that it comes from deeper within the planet. But for it to move from deeper within to the top means a fluid (an aquifer), not an ice (either that or serious tectonics dragging up 500 tonnes an hour!). And given that Pluto's crust provides pre