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Headshot of Emily Lakdawalla

New Horizons releases new color pictures of Charon, high-resolution lookback photo of Pluto

Posted By Emily Lakdawalla

02-10-2015 18:05 CDT

Topics: trans-neptunian objects, New Horizons, pretty pictures, Pluto, Charon, dwarf planets beyond Neptune

Now that New Horizons is regularly sending back data, the mission is settling into a routine of releasing a set of captioned images on Thursdays, followed by raw LORRI images on Friday. The Thursday releases give us the opportunity to see lovely color data from the spacecraft's Ralph MVIC instrument. This week, the newly available color data set covered Charon.

Wow, what a fascinating moon! Look at how many different shades of red cross its surface. Look how different the more-cratered, higher-elevated north is from the smoother, lower south. It's a crustal dichotomy much like Mars'. Look how red Charon's pole is. Look how varicolored its craters are.

Color global portrait of Charon from Ralph MVIC


Color global portrait of Charon from Ralph MVIC
New Horizons captured this high-resolution enhanced color view of Charon just before closest approach on July 14, 2015. The image combines blue, red and infrared images taken by the spacecraft's Ralph/Multispectral Visual Imaging Camera (MVIC); the colors are processed to best highlight the variation of surface properties across Charon. Charon's color palette is not as diverse as Pluto's; most striking is the reddish north (top) polar region. Charon is 1,214 kilometers across; this image resolves details as small as 2.9 kilometers.

The more cool photos I see of Charon, the sadder I feel about our limited photo coverage of the Uranian moons. They're all (except Puck and Miranda) similar in size to Charon, and possess tantalizing hints of similar landscapes. But Voyager 2 flew far from any of them (except Miranda).

Colors and sizes of Uranus' moons

NASA / JPL / Ted Stryk

Colors and sizes of Uranus' moons
The six largest moons of Uranus, to scale with each other, showing their relative colors and brightnesses. From left to right: Puck, Miranda, Ariel, Umbriel, Titania, and Oberon. Color data is from Voyager 2, except for tiny Puck, whose color is derived from Hubble data.

Another of this week's releases compares the colors of Pluto and Charon. They processed the color layers the same way for both worlds in this montage in order to show you how different are the brightnesses of Pluto and Charon -- and how similar are the colors of Charon's north pole and Pluto's dark equatorial regions. What is going on to make that happen, I have no idea.

Pluto and Charon in enhanced color from Ralph MVIC


Pluto and Charon in enhanced color from Ralph MVIC
A composite of enhanced color images of Pluto (lower right) and Charon (upper left), taken by New Horizons as it passed through the Pluto system on July 14, 2015. This image highlights the striking differences between Pluto and Charon. The color and brightness of both Pluto and Charon have been processed identically to allow direct comparison of their surface properties, and to highlight the similarity between Charon's polar red terrain and Pluto's equatorial red terrain. Pluto and Charon are shown with approximately correct relative sizes, but their true separation is not to scale. The image combines blue, red and infrared images taken by the spacecraft's Ralph/Multispectral Visual Imaging Camera (MVIC).

I waited to post these until today in order that I could see what else would show up on the mission's raw image website. MVIC images are not included in the raw image releases. There were eight new photos today, all part of a high-resolution portrait of Pluto's atmosphere taken about three hours after closest approach, with Pluto about 200,000 kilometers away. I don't know if there will be more images in this portrait or not, but I've combined today's new frames with ones that were released last week to make this lovely partial portrait.

Looking back at Pluto: high-res mosaic (partial product)

NASA / JHUAPL / SwRI / Emily Lakdawalla

Looking back at Pluto: high-res mosaic (partial product)

Here is a visual index of what LORRI images have been released to the raw images website so far. If you look down the right-hand side, you'll see a lot of text. At the resolution at which it's embedded, the text is not legible. But it gives you a sense of how much more we have to wait for: blue text signifies observations for which we have seen images, and gray text signifies image sets that have not yet been downlinked and released. There is so much more to come. And this is just for Pluto! Now to create a similar catalog for Charon and the other moons....

Catalog of New Horizons' close-approach images of Pluto as of October 2, 2015

NASA / JHUAPL / SwRI / Emily Lakdawalla

Catalog of New Horizons' close-approach images of Pluto as of October 2, 2015
New Horizons will take a year to return all its science data to Earth. This image compiles the data released for Pluto from the period of 48 hours around closest approach to date. Text at the right side gives an idea of what kinds of data are missing in between the images already returned to Earth. Images are taken as part of specific science observations. If any data from an observation has reached Earth, the text for that observation is blue. The numbers for time, range, and resolution represent the actual metadata for the first image taken in any observation. Gray italic text represents observations that were commanded, but for which data have not yet appeared on the raw images website. This text comes from a table of planned observations given to Emily Lakdawalla by Leslie Young in July 2014. Times, ranges, and resolutions in that document are not precisely correct; they may be off by the actual values by up to ten minutes, thousands of kilometers, and tens of meters, respectively. There is no public information regarding how many images are supposed to be in all of these observations. Observations for which data are on this compilation may include more images not yet returned from the spacecraft. New Horizons LORRI images can be found here. The click-to-enlarge version of this image shows the data at 25% resolution; click here for a full-resolution PNG version.
See other posts from October 2015


Read more blog entries about: trans-neptunian objects, New Horizons, pretty pictures, Pluto, Charon, dwarf planets beyond Neptune


Josh: 10/02/2015 07:19 CDT

Hmmm...Charon appears to have a quartlet of youngish, HUGE, shallow craters near its north pole that practically intersect each other, and a bizarre pit towards its eastern terminator that is surrounded by jumbled terrain...neither hemisphere looks nearly as old as the solar system. And is there a reason why all these round icy moons like erupting from their south poles?

Josh: 10/02/2015 07:21 CDT

Almost forgot...whatever that pit is, it interrupts the huge canyon that straddles most of the rest of Charon. Wonder why...

Karen: 10/03/2015 04:17 CDT

@Josh - There's a number of pits in the southland terrain, most famously the "mountain in a moat". Makes me wonder if we're seeing the after-effects of volatile-loss subsidence. After all, given how fast Pluto is losing volatiles like nitrogen, it amounts to a pretty vast amount of crust subsidence over time. If Charon once underwent the same thing, there's many things that could explain such pits, such as a formerly floating ice crust settling into old, deep craters or heavier crust sections (such as with mountains) settling further than thinner sections. The southland also has the sort of look (relatively flat, broken by undulating rifts) that we've come to associate with rigid water ice crusts floating atop a "fluid" layer (nitrogen ices at these temperatures flow rather well) Perhaps the concept has stuck in my head too much to the detriment of considering other hypotheses, but after seeing Sputnik, I can't help but think of these worlds as water ice floating atop (or at least formerly floating atop) convecting/flowing nitrogen ice mantles (with Sputnik being a location where it's exposed to the surface - not coincidentally also the point nearest Charon). Because during formation of KBOs, water ice would have cooled long before liquid nitrogen solidified (excepting a thin vacuum-frozen nitrogen crust), and being denser, would have sunk, leaving the water ice in the interior and the nitrogen on the outside - but after the nitrogen froze, it became denser than the water ice, allowing entrained water ice chunks to reach the surface, along with impact-deposited water ice, building up a partial or complete ice crust. This would be heavily deformed by the mantle flow (driven by some combination of internal heat, sublimation, and thermal cycling) shifting chunks of ice crust around in full-fledged plate tectonics. Charon being a moon is of course a complication, and the details of how that would play out depend on her formation mechanism, which is still debated.

Josh: 10/03/2015 07:37 CDT

Just to clarify, dense is nitrogen ice? I couldn't find a density for it anywhere...all I found was that liquid nitrogen has a density of .807 g/ml. That's really aggravating when you are trying to calculate whether a surface nitrogen crust (which Pluto does not seem to have anyway judging from the crater count...too high for a flowing crust, too low for one without recent geology) would hypothetically be able to withstand the tremendous atmospheric erosion Pluto has undergone. Never thought about the possibility of a SUBSURFACE nitrogen layer, though...I had assumed that the mountain had a near surface pool of water (also possible in view of Charon's relatively young surface age) that erupted/moved, causing the mountain it was supporting to collapse. Who knows...maybe BOTH processes have occurred on Charon.

Karen: 10/03/2015 08:00 CDT

Densities are always so tricky. It depends on the nitrogen phase (there's a couple options), pore space, concentrations of other ices mixed in (methane, carbon monoxide), temperature, and pressure. But if we assume that anything at depth over geological timeperiods has lost most of its porosity, assume crystalline rather than glassy phases, relatively low methane concentration, etc it comes out solidly heavier than water ice in the same conditions. At its triple point it's 1,027 g/cm3. Water becomes less dense as it freezes but nitrogen becomes significantly more dense (again, barring pore space and phase issues - vacuum-frozen nitrogen is more like a fluff, and phase transition from glassy to crystalline can be practically explosive), so it leads to some potentially interesting issues during formation. Near-surface water on Pluto would be really weird, let alone on Charon. They're incredibly cold. They're mutually tidally locked so they're not imparting energy to each other except indirectly (for example, mass redistributions caused by evaporation/condensation or nitrogen-loss sublimation could in turn cause secondary tidal heating). And below Pluto's water ice appears to be nitrogen ice - you can see the crater punch-throughs near Sputnik. So how one would get a layering of "something"->nitrogen ice->liquid water->water ice, well, I have trouble picturing any scenario that could create that. ;) But it could be different on Charon, we have no evidence of a shallow nitrogen mantle-sea existing there at present.

Karen: 10/03/2015 08:02 CDT

Oh, and phase transitions in nitrogen aren't the only type that could be at work on Pluto - Pluto's water ice should be predominantly Ice XI, but if warms up enough it can transition to Ice Ic or Ice Ih. There's so many potential forces at work that could be sculpting these landscapes... beautiful, beautiful complexity.

David: 10/03/2015 02:39 CDT

There are many features on Charon that (to my untrained eye) look like very old, rather shallow, circular structures, which — if they are in fact the remains of impact craters — suggest a rather dramatic history of events which have all but erased (and, no doubt, in some cases have totally erased) these evidences of ancient impacts.

DavidC: 10/03/2015 05:17 CDT

As a non-expert, the appearance of Charon makes it seem plausible to me that the Pluto-Charon system formed when the two bodies collided in a glancing blow, dissipating enough kinetic energy to leave them gravitationally bound. At least this seems a way to account for both the fracture and the northern coloration on Charon, and perhaps also some of the features on Pluto.

Karen: 10/04/2015 09:32 CDT

@DavidC Theia struck Earth at a "glancing blow". On the scale of planetary collisions, there really isn't any such thing as a non-obliterating glancing blow. The energies released are tremendous, as is the energy to re-accrete and relax back into a sphere. None of the original surfaces from either body would be present today after such a collision.

PaulFR: 10/04/2015 03:58 CDT

@Karen You write "Sputnik is not coincidentally also the point nearest Charon". I've thought since the first pictures of Sputnik that if it would be the spot closest to Charon there could be a causal relation between it and (interactions with) Charon. But nowhere could I find information about which spot on Pluto and which spot on Charon are closest together. But because Pluto and Charon are both tidally locked which each other these spots must exist. Can you give a link to such information?

DavidC: 10/04/2015 06:50 CDT

@Karen, many thanks for replying. Since two passing bodies can miss each other arbitrarily closely, they can also collide with an arbitrarily small collision, which is what I mean by a glancing blow. The collision between Theia and proto-Earth was not a glancing blow in that sense, as the overlap of the trajectories of the two bodies was substantial.

Arbitrary: 10/05/2015 05:45 CDT

Is there a way to format the blog so that the text lines don't get as long as the largest image posted is wide? I sometimes have to copy paste the text to a word processor to be able to read it.

Karen: 10/05/2015 09:30 CDT

@DavidC "they can also collide with an arbitrarily small collision" Which would correspondingly have an arbitrarily small effect on their velocities. It's simply not possible to have a relevant effect on their velocities and not impart a resurfacing-level amount of energy to both. These are objects meeting at many thousands to many tens of thousands of meters per second relative velocity. @PaulFR

Josh: 10/06/2015 05:42 CDT

Upon reviewing the uranian satellite pics, it quickly becomes apparent that in spite of their low resolution, most of the large Uranian satellites have FAR more craters than Charon. Ariel is the exception, being seemingly quite close to Charon in age and much younger looking than anything else in their size range in the solar system...I wonder if both Charon AND Ariel are geologically active, and if so why them and not Uranus's other, similarly built large moons...hmmmm....

Justin: 10/20/2015 03:00 CDT

Why is it red? 7th Grade

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