New Horizons probe successfully arrives at Pluto

[Borgholio]

How close together they are doesn't really have much effect on heating. What does matter is changes — one of the best examples being Jupiter's moon Io. It's in a constant tug-of-war between Jupiter and the other three Galilean moons, and it's in orbital resonance with two of them, preventing its orbit from becoming more circular and stable. These constant changes in the pull of gravity are what causes tidal heating, so we end up with a moon that has the most volcanoes anywhere in the solar system.

Sure, but Pluto and Charon are closer than any other planet (dwarf planet, whatever) / moon combination in the solar system. Would not the relative strength of the gravitational pull make up for lack of motion between the two bodies?

[SpottedKitty]

Would not the relative strength of the gravitational pull make up for lack of motion between the two bodies?

Not really, unless the two were much closer together. There's a limit in astronomy called the Roche Limit, that describes what happens if an orbiting moon gets too close to its parent body — the tidal force is more than the moon's surface gravity, and it begins to break up. For a system like Pluto/Charon, it's stable, so there aren't any changes over long time periods. Unless something drastic happens to the solar system, they'll probably stay that way indefinitely.

[Borgholio]

Hmm...so what else could be causing it then, I wonder. It never gets close enough to Neptune, and the other moons are much smaller than Charon. It can't have residual heat since it's so small. Must be an alien fusion reactor at the core of the planet.

[InsaneTD]

Maybe when rocks hit the surface they cause enough great to enter the system to cause liquefaction to the surface. Could possibly mean that things that should leave craters don't, since the liquid reaches a reasonably even surface before refreezing.

[Borgholio]

If Pluto is indeed mostly ice (like Europa) then that makes sense. Any asteroid large enough to leave a crater will melt enough of the water to fill it in. The surface isn't rock afterall...

[Highlord Laan]

Closeup of some mountain ranges that are over 2 miles in height...and they're fairly young too. Pluto may still be somewhat geologically active.

Any signs of the Migou?

[SpottedKitty]

If Pluto is indeed mostly ice (like Europa) then that makes sense. Any asteroid large enough to leave a crater will melt enough of the water to fill it in. The surface isn't rock afterall...

Ah, but at those temperatures, water ice behaves like rock, so that makes up a lot of Pluto's "bedrock" at fairly shallow depths. On top of that, though, the surface seems to be a mix of everything; water ice, other more fragile ices, dust and rock rubble... I think we're going to have to wait for the raw, uncompressed data to make sense of all this.

Also, remember that Europa's smoothness is most likely due to the possible subsurface liquid water, which wouldn't be there without tidal heating. Pluto's surface and subsurface conditions are different enough there must be something else going on there.

[Napoleon the Clown]

Pluto lacks sufficient atmospheric pressure for water to exist as a liquid. The atmosphere may be thick enough to cause difficulties with estimating its diameter from here on Earth, or in LEO, but it's nowhere near thick enough to offer all three phases of matter to water. While there's pressure acting on it, sure it could be a liquid. But then it would sublimate, violently most likely, as nothing is able to push on the molecules hard enough to stop them from scattering. Think of what happens when you vent a pressure cooker too quickly. You've got liquid water that's well over 100* C because there's enough pressure on it that it can boil at a higher temperature. Bring that pressure back to 1 atmosphere, and suddenly the water is substantially hotter than liquid water can be at that pressure.

Something is going on, but it isn't water ice getting melted.

[Borgholio]

New data and images are supposed to be released later today. Maybe they'll shed some light on this.

heh, who am I kidding...I vote for the new data raising even more questions.

[Simon_Jester]

Pluto lacks sufficient atmospheric pressure for water to exist as a liquid. The atmosphere may be thick enough to cause difficulties with estimating its diameter from here on Earth, or in LEO, but it's nowhere near thick enough to offer all three phases of matter to water. While there's pressure acting on it, sure it could be a liquid. But then it would sublimate, violently most likely, as nothing is able to push on the molecules hard enough to stop them from scattering. Think of what happens when you vent a pressure cooker too quickly. You've got liquid water that's well over 100* C because there's enough pressure on it that it can boil at a higher temperature. Bring that pressure back to 1 atmosphere, and suddenly the water is substantially hotter than liquid water can be at that pressure.

Something is going on, but it isn't water ice getting melted.

For that very reason, it seems unlikely that the water-ice layer of Pluto is reliably exposed to the surface, because literally anything that CAN vaporize or melt at lower temperatures and pressures than water (e.g. methane or nitrogen) would tend to redeposit over the layer of water-ice.

The end result would be that water is Pluto's equivalent to rock, a substance which is always solid unless it gets hit by a comet or shot out of a volcano or exposed to some other exotic high-energy process. And water would therefore be 'bedrock.'

But the water that is the planet's bedrock would be covered in a variable-thickness layer of other substances (ammonia, nitrogen, methane, etc.) that melt more easily and form the analogues to the Earth's oceans and topsoil.

[Not saying Pluto EVER had liquid oceans of any kind- but for purposes of just determining where the surface of the planet is, most of the Earth is covered in a kilometer or two of water layered on top of its bedrock. On Pluto there might be a solid layer of methane ice instead or something, but the effect on the surface level is similar.]

And as on Earth, these other substances would tend to 'flow' around (at least on geologic time scales) and soften the outlines of any major terrain features created by the shape of the underlying un-meltable, un-vaporizable water 'bedrock.'

[SpottedKitty]

Things that make you go "hmm"...

Is anyone else looking at the latest closeup of Tombaugh Regio reminded of the canaloupe terrain on Neptune's moon Triton?

And we have another moon closeup. Well, at least Nyx is a bit more round-ish than Hydra is.

[Darmalus]

Some condensed info on Pluto, cryo-geology is pretty neat. Volcanoes of nitrogen!

https//www.youtube.com/watch?v=SeIyO1J2rnA

Edit: I give up.

[Irbis]

You want http:// in front of the link, not https// .

[Batman]

Https works just fine if you remember to include the :

[Irbis]

Https works just fine if you remember to include the :

Test it and you will see that no, it doesn't, at least with the youtube embed plugin version used here.

Said plugin is also defeated by such simple things as adding start time or playlist to the video, unless you need to do it in some obscure arcane order. Nothing but just http and address stripped of anything but ?v= will work.

[Batman]

https://www.youtube.com/watch?v=SeIyO1J2rnA

Works fine for me. Not everybody posting links wants to embed.

[SpottedKitty]

Argleblargle.

Has this cut-cut-cut-hyooooooogecaption-cut-cut video style become A Thing now in the US? I could barely watch it right through to the end. Interesting and informative, but he sounded like he was trying to be a used car salesman. Or maybe "Explore this KBO now and we'll throw in a FREE!!!! — yes, FREE!!!! — set of these great ginsu knives!"... Honestly, if the clip had been much longer I think I might have got motion sickeness.

[jwl]

Jump cuts are more of a youtube fashion than anything else.

[dragon]

not sure it's been mentioned but the found signs of flowing ice on Pluto, kind of cool if you think about it. Pun intended.

New Horizons discovers flowing ices in Pluto’s heart-shaped feature. In the northern region of Pluto’s Sputnik Planum (Sputnik Plain), swirl-shaped patterns of light and dark suggest that a surface layer of exotic ices has flowed around obstacles and into depressions, much like glaciers on Earth. Credits: NASA/JHUAPL/SwRI

NASA’s New Horizons mission has found evidence of exotic ices flowing across Pluto’s surface, at the left edge of its bright heart-shaped area. New close-up images from the spacecraft’s Long-Range Reconnaissance Imager (LORRI) reveal signs of recent geologic activity, something scientists hoped to find but didn’t expect.

“We’ve only seen surfaces like this on active worlds like Earth and Mars,” said mission co-investigator John Spencer of SwRI. “I'm really smiling.”

The new close-up images show fascinating detail within the Texas-sized plain (informally named Sputnik Planum) that lies within the western half of Pluto’s heart-shaped region, known as Tombaugh Regio. There, a sheet of ice clearly appears to have flowed—and may still be flowing—in a manner similar to glaciers on Earth.

link

[Borgholio]

Glaciers. That could easily explain the lack of impact craters.

[SpottedKitty]

Glaciers. That could easily explain the lack of impact craters.

<nod> That ties in nicely with something that was said in the Sky At Night special mentioned upthread — while water ice behaves like rock in Pluto's environment, more exotic ices like nitrogen, methane, etc. are softer. That should mean they're more likely to be able to flow like water ice glaciers on Earth, even though the gravity is much lower, so the forces encouraging the ice to flow are much lower. Fascinating stuff.