New Horizons: Near Encounter Phase Options

[Habukaz]

I am starting to wonder if Charon has some Triton-esque terrain, too. Take a look..





Not much solid evidence for many well-preserved impact craters, which is interesting.

[admin edit]

[Sherbert]

Agree. Only evidence for a few really big ones. That may be resolution or the smaller ones have been covered over or changed by resurfacing events.

[Superstring]

Charon does look like a Uranian moon from this resolution. We already know it's similar in size and density as well. It would be wonderful if closeup images of Charon tell us more about them.

[Sherbert]

Just looked at the latest Charon image again and that "crater" at 6-7 O'Clock appears to me to have a plume of darker material in the direction of the limb and a generous observer might say a smoke trail similar to a volcano can be seen. Impact crater or Caldera, the old question when looking at lower resolution images, even higher ones from Ceres are not conclusive. While in such an extravagantly, unfounded, speculative vein, the vast long Chasm running from 4 to 6 O'Clock, a rift valley? Are there, or were there, continents of Water Ice moving on a mantle of slush made up of super volatiles. At this point Charon is turning out to be a real conundrum. Pluto seems to fit the favoured theoretical models quite nicely, nobody seems to have a good handle on what's going on at Charon.

[Ian R]

I think Charon's going to be the biggest surprise from this flyby. I may be wrong, but perhaps we're looking at an icy version of Io here.

[Sherbert]

I think Charon's going to be the biggest surprise from this flyby. I may be wrong, but perhaps we're looking at an icy version of Io here.

It may not be now, but before the two bodies became tidally locked, that is plausible I suppose. That might mean that what look like impact craters on Pluto might be ancient Calderas. especially the big circular features we saw on the Charon facing face a couple of days ago.

EDIT: It might also explain why Charon is so uniformly "coloured" and the darkness of the polar cap.

[Bjorn Jonsson]

Charon looks somewhat similar to Uranus' moons, at least at this resolution. The chasm seems comparable to features seen on Ariel and Titania.

Just looked at the latest Charon image again and that "crater" at 6-7 O'Clock appears to me to have a plume of darker material in the direction of the limb

I can't see anything plume-like anywhere.

Meanwhile, on Pluto in the latest image (the one obtained at a distance of 2.5 million km), some of the terrain in the lower half of the image and left of center (at approximately 7 o'clock where there are alternating patches of bright and darker terrain) is starting to remind me a bit of the weird looking terrain seen in hi-res images of Mars' polar regions ("Swiss cheese features") where sublimation is a significant process. The only problem is that the Martian features aren't big and wouldn't even be close to visibility at the resolution of the most recent NH Pluto image.

[PDP8E]

Its amazing what you can do when if you write scripts (and get out of work early!)
Here are the 2nd set of images from July 11, 2015

[Bjorn Jonsson]

Here is yet another version of my map of Pluto, this time incorporating the recently released image that was obtained at a range of 2.5 million km (the one that can be found here at the NH website). Apparently it was obtained on 2015-07-12 at 08:46. As usual, longitude 0 is at the left edge of the map.



The map now has much better coverage of parts of the terrain that will be imaged at high resolution tomorrow, including the northeast half of the bright region near the center of the map.

[volcanopele]

Thanks for that map. The bright terrains near the equator definitely look like the patchy ice cap margins we saw at Triton.

[gpurcell]

Given that big and uneroded crater on Charon, I suspect it will end up being a heavily cratered body with limited to no resurfacing that looks rather similar to Oberon.

[Sherbert]

I have circled the feature on Charon in this image. It has to be speculation at these resolutions, but one also never knows. Personally, it looks very much like a textbook impact crater, but the heat generated must have resulted in some Cryovolcanic activity.

https://www.flickr.com/photos/124013840@N06...eposted-public/

[JRehling]

I wonder if Charon has a mainly-ancient surface with most of its internal heat having vented through the north polar area, just as Enceladus has a mainly-ancient surface with most of its internal heat venting near its south pole.

It seems like too much of a coincidence for Charon's biggest impact basin to have hit its north pole so squarely, so I would guess that the dark spot is volcanic. Another possibility is that it is impact-related and some sort of tidal dynamic moved the rotational pole from another place to that location. Or, it could be purely the result of volatile transport.

[nprev]

Obviously there must have been some local melting after the impact, but impossible to say if cryovolcanic activity would result. Much better imagery will be required to determine that.

[Phil Stooke]

I would prefer to bet on a climate origin of the dark spot. As Charon rotates at the current season, the dark spot occupies most of the area that is permanently illuminated and therefore a bit warmer than lower latitudes. Any ice (whatever its composition) which can sublime off that region and condense further south will be removed. As seasons change the dark spot may expand and contract, possibly leaving some of those concentric dark fringes.

Phil