Icy Volcanoes May Erupt On Pluto (space.com)

An anonymous reader writes: The New Horizons probe may have discovered two possible ice volcanoes on the surface of Pluto. "These are two really extraordinary features. Nothing like this has ever been seen in the solar system." Oliver White, a New Horizons postdoctoral researcher with NASA's Ames Research Center in California said. The mountains have been informally named Wright Mons and Picard Mons, and at their crests, each peak hosts a central crater, reminiscent of peaks called "shield volcanoes" on Earth. "Whatever they are, they're definitely weird" — 'volcanoes' is the least weird hypothesis at the moment," White says.

Comments

Heat source?

[Applehu Akbar]

So in the absence of tidal flexing in Pluto's vicinity, where's the heat coming from?
http://news.sciencemag.org/spa...

Re:Heat source?

[Anonymous Coward]

FTA:

"Scientists don't yet know what could be generating the heat inside Pluto necessary to create a volcano on the surface. One possibility, also presented at the conference, is that an ammonia-water slurry mantle lies beneath the surface, according to a statement from AAS. The research, performed by graduate student Alex Trowbridge and professor Jay Melosh, of Purdue University in Indiana, suggests that, as cooler material sinks through the subsurface layers, hot material might rise, leading to geological activity that could include cryovolcanism.

Another possibility, which White focused on, has to do with a gradually cooling rocky core, originally heated during the dwarf planet's formation. The heat required to melt ices would be significantly lower than those required to release rock, allowing the gradual mobilization of material that could, in theory, erupt through a volcano."

Re:Heat source?

[Rei]

Lots of possibilities.

1. Residual formation heat or heat from major ancient impacts. Low, but when you're talking about the tiny inputs needed for cryogenic systems, it's possible.

2. Radiothermal heating. Again, low given Pluto's small size, but see #1

3. Solar heating. Again, see #1.

4. Chemical reactions in Pluto's rock. This is what's believed to be a major contributor to Enceladus's oceans (serpentinization of rock leading to a "soda sea")

5. Subduction. The subduction of denser materials and the rising of lighter materials is an energetically favorable process. In particular, during cooling liquid nitrogen would have tended to rise over water ice (water ice being denser than liquid nitrogen), but solid nitrogen (when compacted) is denser than solid water, so after it froze it would be energetic for it to subduct.

6. Relaxation. Any layers in non-gravitational equilibrium form due to Pluto's history relaxing to a more gravitational equilibrium (regardless of whether subduction is occurring) yields a release of energy.

7. Transitions between different ice phases. At temperatures and pressures we're used to most matter that we encounter in our daily lives only comes in one crystalline phase. But the various ices found on Pluto have numerous different ice phases, with different energies and densities associated with them. Most of these can metastably persist for long periods of time but transition when conditions favor doing so. The transitions can even sometimes be explosive.

8. Solar wind-driven sublimation. At one point it was thought that the solar wind had taken off nearly a thousand meters of nitrogen ice from Pluto, which would of course cause a redistribution of Pluto's mass and resettling. However this now seems unlikely as the extent of Pluto's atmosphere has been refined downward, reducing the rate of mass a thousandfold.

And many more - there are vast numbers of possibilities. That said, calling these ice volcanoes still sounds weird to me. Nitrogen, methane, and carbon monoxide ices are too readily flowing to support structures this high - it was well known in advance of the mission that any high contours would have to be water ice. But Pluto appears to have a mantle of nitrogen ice (exposed at Sputnik) under a water ice crust (possibly with layers of denser high pressure water ices underneath the nitrogen, although who knows). So how are flows of liquid water coming up through easily-flowing nitrogen ices? That doesn't make any sense to me. Also, that surface texture doesn't look anything like lava flows, at least on the large scale (some of it kind of looks like pillows, but there's no logical reason that pillows could be produced on such absurdly large scales on Pluto). The stuff nearest the "crater" looks tectonic. Honestly, I'd be less surprised to learn that it's some kind of huge frost heaving structure rather than a cryovolcanic one, maybe driven by solid-state ice phase transitions. Frost heaving tends to produce "hummocky" terrain like is seen in the pictures, and some frost heaving structures have central "craters". Another possibility would be mass loss rather than eruption. Perhaps there was a pocket of nitrogen, methane, or carbon monoxide ice long ago embedded in a large chunk of water ice that has since all sublimated away, leaving a giant collapsed sinkhole (which is being interpreted as a "crater"). Maybe it even happens regularly, some lighter ices seeping in, building up a chamber, then subliming away. Yet another possibility would be mildly analogous to pseudocraters on Earth - perhaps there are explosive events there (such as self-propagating solid state ice transitions, or rapid vaporization of "warm" nitrogen/methane/carbon monoxide ices suddenly released from pressure) that eject material and form a structure looking like a volcanic crater without actually having volcanic "roots" feeding liquid water in.

Re:Heat source?

[Coren22]

Is it possible that it is tidal heating from Pluto's satellites? Charon is pretty big, could it induce tidal heating in Pluto, and the inverse?

http://www.space.com/16535-plu...

Re:Heat source?

[Rei]

No, Charon and Pluto are tidally locked. That said, any changes in mass distribution on one can impart energy to the other.

Re:Heat source?

[Coren22]

I was not aware of that, thank you.

Pluto Climate Change?

[BisuDagger]

Should we start being concerned about the effect of climate change on Pluto and how it may affect us 2 millions years from now?

Least Weird Hypothesis?

[R3d M3rcury]

FTFA:

"Whatever they are, they're definitely weird — 'volcanoes' is the least weird hypothesis at the moment"

Oh c'mon! What's the most weird hypothesis at the moment?

Since a new Star Wars movie is opening in a few weeks, I'll go with "Unshielded Thermal Exhaust Port." And add the obligatory, "That's no dwarf planet..."

you know what this means?

[The_Rook]

on pluto, we would be molten lava creatures.