New Horizons at Pluto

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Image courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

As a layperson, the features on Charon that stand out:

The black eye (unoffically named Mordor) that dominates the upper hemisphere.

The differences in the upper and lower hemispheres -- bound by the linear feature that kind of traces maybe 20° S across most of this face.

The feature almost at the terminator to the right of and somewhat lower than the "Mordor" feature. Hopefully LORRI got a better orientation on whatever that is.
 
Trebuchet said:
My first thought was a young surface, but it might be more likely that it's so far out there that there aren't many impactors.
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There's an interesting idea. Because lots of internal heat seems really strange on a small icy body.

But is it plausible? There's plenty of potential impactors out there. Lumps of ice. And never any large planet to sweep them up.
 
How much (if much at all) does Pluto's surface temperature change from its furthest point to its nearest point?

In other words, could it be a case of something defrosting when it's within Neptune. so smoothing the surface?
 
Craig B said:
Trebuchet said:
My first thought was a young surface, but it might be more likely that it's so far out there that there aren't many impactors.
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There's an interesting idea. Because lots of internal heat seems really strange on a small icy body.

But is it plausible? There's plenty of potential impactors out there. Lumps of ice. And never any large planet to sweep them up.
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NASA says there would be fewer impactors that far out, but there still aren't as many craters as expected. https://twitter.com/NASANewHorizons/status/621437916783484928

They also speculated a bit on why/how the surface could be so young: https://twitter.com/NASANewHorizons/status/621439947170578432.
 
Craig B said:
There's an interesting idea. Because lots of internal heat seems really strange on a small icy body.

But is it plausible? There's plenty of potential impactors out there. Lumps of ice. And never any large planet to sweep them up.
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Internal heat would be from the tidal friction created by Charon I expect.
 
Samson said:
Internal heat would be from the tidal friction created by Charon I expect.
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Phil Plait says, no.

The two bodies are tidally locked, lessening tidal friction. Otherwise you'd see the Earth heated up from the Moon. The current hypothesis is internal radioactivity. I take it that is very tentative, but we'll see.
 
Skeptic Ginger said:
Phil Plait says, no.

The two bodies are tidally locked, lessening tidal friction. Otherwise you'd see the Earth heated up from the Moon. The current hypothesis is internal radioactivity. I take it that is very tentative, but we'll see.
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The Earth isn't tidally locked to the Moon and is heated by it. However that heating is only a very small proportion of Earth's energy budget.

http://www.skepticalscience.com/heatflow.html
 
It's too bad the pictures are all black and white. If they were in color, we might be able to see the difference between the desert areas and the forests.
 
My guess is that there would not be much internal heat in Pluto as it is so much smaller than the moon. Any heat would be rapidly lost. I like the idea that the surface partially melts when Pluto gets nearer the sun.
 
Heat could be generated a few ways.

First, never underestimate the power of collisions. Even small collisions, if there are enough, could generate significant heat.

Second, tidal friction with Uranus. Not a constant source, no, but maybe an occasional one?

Third, radioactive materials. I've heard speculation about that on various fronts. With a half-life of around 4 ga, some uranium isotopes would be going strong.

The difference between the northern and southern hemisphere of that moon is really very striking. Not just texture, but variability--the northern hemisphere appears more rugged, and has a greater number of light and dark spots than the southern.

Maybe the planets ricocheted off one another, and were captured in each other's gravity? I'm not up on my planetary collision physics, but I suspect that would be a poor explanation--anything slow enough to be captured would be a direct hit, not a glancing blow, and anything fast enough to be a glancing blow wouldn't allow for capture (or would completely liquify things).

Any sense of where Pluto is in relation to this moon? As presented, it seems we're supposed to accept Mordor as the northern pole relative to the plane of the orbits.
 
sts60 said:
Charon is really interesting.
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Absolutely!

steve s said:
http://ichef.bbci.co.uk/news/976/cpsprodpb/10099/production/_84298656_84298655.jpg


11,000 foot peaks, and 150 miles without any impact craters. I can't wait for more photos to come in.


Steve S
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Sorry but You're going to have to. :)

Trebuchet said:
My first thought was a young surface, but it might be more likely that it's so far out there that there aren't many impactors.
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There should be sufficient KBOs to crater the surface more than is seen, much speculation about vulcanism and atmospheric weathering.

Dinwar said:
Just wild speculation, but could the system have originally been one body, which was hit by something? That's how our moon was likely formed. If that happened, say, 100 ma, it would account for the youthful surface. The re-solidification could also account for some of the weird features, like the hummocky features on the right-hand side of the high-res Pluto image and the hills (water volcanoes?).
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Quite possibly, with residual heat allowing for vulcanism. Of course there's a lot of water ice on the surface too.
 
Dinwar said:
Any sense of where Pluto is in relation to this moon? As presented, it seems we're supposed to accept Mordor as the northern pole relative to the plane of the orbits.
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That's a good question.

New Horizons' trajectory generally followed the plane of the ecliptic (the plane containing the major planets). Pluto and Charon orbit about a barycenter with the plane of those orbits roughly perpendicular to the ecliptic -- with an ~133° axial tilt.

Following the the IAU nomenclature for dwarf planets and the right hand-rule, Charon's positive (a.k.a. North for big-boy planets) pole would be ~133° from the ecliptic -- roughly pointing toward the inner solar system.

I really don't know if how the LORRI instrument was oriented or if the image was corrected to reflect the plane of the solar system or the plane of the barycenter.
 
catsmate said:
Quite possibly, with residual heat allowing for vulcanism. Of course there's a lot of water ice on the surface too.
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Fractional distillation may account for this as well. As the water-ice formed, the concentration of non-freezing chemicals would increase. If you put liquer in the freezer it'll form ice crystals (eventually). Scoop those out, and the remaining liquid is more alcoholic than the original. Same principle applies here; the question is, to what extent?
 
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