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Charon: The Mega-Moon With a Mountain in a Moat

Pluto’s largest moon, Charon, is almost as enigmatic as Pluto. As NASA’s New Horizons spacecraft helps unveil the underworldly moon, most of its features are turning out to be more puzzling than expected.

Early images showed an unexpectedly dark polar cap, which scientists think could be the result of material migrating over from Pluto. And an image released July 15 revealed that the 1,200-kilometer-wide world appears to have a surprisingly young surface with tantalizing hints of geologic activity.

“We’re flabbergasted. We really are,” says New Horizons team member Bonnie Buratti of the Jet Propulsion Laboratory. “To tell you the truth, Charon looks more like I would have expected Pluto to look.”

As seen in this image released July 15, Charon's surface is full of surprises. (Photograph by NASA/JHUAPL/SwRI)
As seen in this image released July 15, Charon’s surface is full of surprises. (NASA/JHUAPL/SwRI)

The latest image release zooms in on a portion of Charon’s surface that lies kind of near the moon’s equator. Snapped by New Horizons as it approached the Pluto system on July 14, the image – unsurprisingly – has scientists completely baffled.

In it, Charon’s surface is smooth, with a smattering of craters and cracks – and there’s a bizarre mountain rising out of a depression that has been called a “mountain in a moat.”

“It looks like somebody just dropped a giant boulder on Charon,” Buratti says.

So far, scientists have no idea what’s going on with the Charonian peak. But, says team member Anne Verbiscer, it does look similar to a feature on another of the solar system’s most curious worlds: The two-toned moon Iapetus, which orbits Saturn. “I find both of them fascinating,” says Verbiscer, of the University of Virginia. She notes an intriguing and speculative connection between the mountain, icy volcanism, and the ground-based detection of a compound called ammonium hydrate.

“Ammonia hydrate acts like antifreeze when mixed with water ice, and can help with making cryovolcanic activities possible on bodies such as Charon and Iapetus,” Verbiscer says.

As for those craters and cracks? The cracks, Buratti says, are faults. She notes that similar-looking fractures have been seen in basins on Earth’s moon – where they’re the remains of lava tubes – as well as on Mercury, where they suggest that the planet is shrinking. But Buratti doesn’t think either of those explanations account for Charon’s wrinkles.  “We really have no idea what to think at this point,” she says.

Then there’s the relative sparseness of craters. Indeed, those missing craters seem to be one of the more perplexing observations the team is wrestling with. “There are fewer craters than we expected, and we don’t know why,” Buratti says.

Together, the cracks and relatively pit-free surface suggest Charon could have been a pretty active world, and nothing like the stagnant, battered chunk of rock many scientists had anticipated. “We expected it to be more of a dead object,” Buratti says. “But there’s some active process on the moon that happened in the past.”

Along with scrutinizing Charon, the team will be keenly studying Pluto’s surface for signs of activity as well. Already, the dwarf planet’s high-contrast, mountainous face is keeping a sleep-deprived New Horizons team busy. “Pluto did not disappoint,” said deputy project scientist Cathy Olkin. “And Charon did not disappoint, either.”


19 thoughts on “Charon: The Mega-Moon With a Mountain in a Moat

  1. I’m amazed at the findings at the Pluto System. I suggest that for the “follow-on” mission for New Horizons, that we program it to sling-shot back into our Solar System and eventually wind up in orbit around Pluto. I have no idea is such a feat is indeed possible but if it is, let’s…”Return to Pluto!”

  2. So…….Is it a planet or a dwarf planet? Most of us learned it was a planet. Can’t we just make it a planet and leave it at that?

    1. whatever sublimation is occurring, it is eclipsed by the sublimation of $$BILLION for pics and info about a radiated, atmospheres hulk in an incomprehensibly distant and common gravitational lock with the pluto thingy and the star Sol.
      Save us from frivolence and lack of attention to our human apocalypse of aging and death every animal, human and otherwise, is infected with.

  3. And this is why it is important to explore, to discover. Never assume that we know everything or that other moons or planets would be boring.

    We need many more missions. The new frontier past Neptune is probably full of surprises… let’s get there with new spacecrafts.

    Closer to home… all these asteroids and comets can teach us alot as well… our exploration has barely begun.

  4. Is anybody else thinking “Empire Strikes Back”…
    the giant asteroid creature that tries to eat the Millenium Falcon.

  5. You can sense the joy that Ms. Drake must have felt as she wrote this article on the latest discoveries from New Horizons. I know I have been thrilled by the impressive success of this mission to Pluto and beyond. This data will be used to write the textbook about Pluto, Charon and the other residents of the Kuiper Belt. This is where our tax dollars should be going. Our future as a species depends on us getting off of the earth. The excitement about this mission reminds me of a speech JFK gave at Rice in 1962. Kennedy was speaking about our national effort in space exploration. He said, “For the eyes of the world now look into space, to the moon and to the planets beyond, and we have vowed that we shall not see it governed by a hostile flag of conquest, but by a banner of freedom and peace. We have vowed that we shall not see space filled with weapons of mass destruction, but with instruments of knowledge and understanding. Yet the vows of this Nation can only be fulfilled if we in this Nation are first, and, therefore, we intend to be first. In short, our leadership in science and in industry, our hopes for peace and security, our obligations to ourselves as well as others, all require us to make this effort, to solve these mysteries, to solve them for the good of all men, and to become the world’s leading space-faring nation. We set sail on this new sea because there is new knowledge to be gained, and new rights to be won, and they must be won and used for the progress of all people. For space science, like nuclear science and all technology, has no conscience of its own. Whether it will become a force for good or ill depends on man, and only if the United States occupies a position of pre-eminence can we help decide whether this new ocean will be a sea of peace or a new terrifying theater of war. I do not say the we should or will go unprotected against the hostile misuse of space any more than we go unprotected against the hostile use of land or sea, but I do say that space can be explored and mastered without feeding the fires of war, without repeating the mistakes that man has made in extending his writ around this globe of ours…” Boldly Go!

  6. For those who have an open mind regarding alternative cosmological models, I’m a distant fan of the Electric-Plasma model.

    According to this model, craters were created due to electric discharges occurring between differently charged bodies. It’s also electrical forces that placed the planets in neat orbits around the sun.

    If you grant this theory, then obviously it becomes fallacious to date a surface based on the number of craters. Instead, it’s an indication of how many times it passed a differently charged body in the past.

    This would mean that one would expect lots of craters on bodies in the inner solar system, the moons of the Gas giants, and even the asteroid fields. However, remote bodies such as Pluto would have far fewer craters.

    I dare to predict, if we ever send a probe to Eris, we’ll also find few, maybe even less craters than on Pluto.

    PS. Before you mock the electric model: When scientists say they’re surprised, it means that they did not find the results their model predicted. A theory is tested by its predictable power. Lately, we’ve often heard astronomers express surprise at new discoveries. They even invented unobservable stuff like dark matter and dark energy to explain away anomalies. (Does anybody remember Ether?)

    All this says that our current understanding of astronomy is fatally flawed, and dogmatically insisting on the current singular paradigm will hinder, rather advance our understanding. Science is suppose to constantly test competing theories, not dogmatically seek to reaffirm the dominating consensus.

    Just saying.

  7. Yes, it is a lump of matter pockmarked with craters and maria and so what?
    and how does this benefit any person, animal, or thing, now or in the future?
    Humans are a over a BILLION years selectively developed and adapted on earth, and thus on earth humans will eternally stay. Humans are hyper-adapted and ultra-senstitive to very specific parameters at or around the surface, at or around specific gravity, at or around radiation levels, at or around gas levels, pressure levels, etc.
    Space is EXTREMELY hostile, EXTREMELY dangerous and OUTRAGEOUSLY expensive to counter the bad effects for even short durations for several folks at a time.

    Yes, Space is NOT a place for humans and never will be, so stop the juvenile dreaming of space and living with dinosaurs and travelling thru “wormholes”.

  8. Actually, I have seen similar impacts when looking at detailed impacts of particles in a air filter. These impacts are tend to create a small indentation in the filter around the fibers of a filter if the particle is relatively heavy, but slow moving as it encounters the resistance of filter.

    1. yes, Jeff, thats probably a good analogy.
      Unfortunately, space fans irrationally promote anything in space as “enigmatic”, “mysterious”, “cool”. To borrow a phrase, it is irrational exuberance over the most mundane photos, yes they are PHOTOS. If only this collective could redirect their energies to matters that impact not space matter, but rather to matters that impact LIFE ON EARTH.
      send me a billion dollars and i’ll tell you things about a tree in the far distance and send you monthly photos of your adopted tree. 😛 Instead of a space shuttle or station, we’ll have the coolest of treehouses.

  9. Maybe the “Dropped a giant boulder” analogy best describes what happened to create the “mountain in a moat” feature. The Kuiper belt is full of such objects, and a slow speed collision with said object could indeed create what the photo shows, displacing surface material and the impactor remaining more or less intact and incompletely buried.

  10. Strange. Responding to comments about the value of exploration. To me the human condition, including how we have evolved delicately over time is directly related to exploration, adaptation and expansion. To deny that exploration including space is not distinctly part of our past and future seems to me to neglect the innovation and discovery that is very the basis of all of our existence and progress to this point.

  11. It is pronounced “karon”, as in the ferryman on the river Styx who takes you to Hades ( most appropriate), so WHY is your announcer saying Sharon??? It’s a hard k sound in Greek and the Greek and Roman myths are the sources of the names for the planets and moons! What!

    ND: Hi, Kathleen. There is a lot of confusion about how to say “Charon.” Everyone pretty much goes with whatever they want (I think I’ve heard at least five different pronunciations). That being said, Charon was named after discoverer Jim Christy’s wife, whose name is Charlene. The link to the Greek ferryman only occurred to him later (a great coincidence!). Anyway, Jim and Charlene Christy were at the Pluto Flyby events, and he clarified the proper pronunciation: You start with “Char” — as in Charlene — and add “on.” Charlene’s comment was pretty charming: “A lot of husbands promise their wives the moon, but mine delivered!”

    Of course, everyone will continue to pronounce Charon however they would like to, and that’s O.K. as far as I’m concerned.

  12. The gravities of Pluto and (S)Charon fought to attract a huge lump of rock. Charon won, hence Moat Mountain. But it was a close fought battle that caused the rock to slow it’s descent onto the surface.. it is still sinking.

  13. I am more interested in the fact that in the wide angle photo, many of the craters appear to be in rows or arcs. Are those craters or calderas?

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