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Pluto’s Large Moon Charon Is Stunning

Remember when we reported that Charon would probably turn out to be an astonishing world in its own right? Well, the newest image released by the New Horizons team suggests Pluto’s largest moon is absolutely that.

Charon is a world of chasms and craters, capped by a darkened pole. NASA/JHUAPL/SwRI
Charon is a world of chasms and craters, capped by a darkened pole. NASA/JHUAPL/SwRI

In the photo, shot from less than 5 million kilometers away, the 1,200-kilometer-wide sphere appears riven with enormous canyons — at least one of which is deeper and longer than the Grand Canyon, said planetary geologist Bill McKinnon of the Washington University in St. Louis in a statement. In addition, Charon’s surface is mottled with impact craters. That alone is not surprising (in fact, craters were one of the team’s top predictions for surface features on Charon), but the size and color are intriguing. One of the crater bottoms appears darker than the surrounding surface; whether this is because it’s made of different material or is simply less reflective isn’t clear yet. And then there’s that mysteriously dark region capping the moon’s pole.

What is clear is that these images will only get better as New Horizons continues to speed toward its July 14 trip through the Pluto system. Soon, we may even be able to see the planet’s four small moons as well. (Learn more about the historic mission to Pluto on the National Geographic Channel.)

Speaking of moons, one of the predictions the team made was that New Horizons would discover at least one more moon orbiting Pluto. So far, no additional moons have been spotted. Unfortunately, that could be due to the July 4 glitch that sent New Horizons into safe mode.

“The one piece of significant science that we did lose due to the safing event was the deepest search for moons,” says team member Mark Showalter of the SETI Institute. Those data would have been taken seven days prior to closest approach. Now, the team will be searching through older data (from 13 days prior) for moons. Those images are taken from about twice as far away, though.

But all hope is not lost yet. New moons might still be discovered, Showalter says, either during the reprocessing of data taken in the last month, or if a new moon serendipitously pops up in another image.

P.S. At 11:23 p.m. tonight, New Horizons will be within a million miles of Pluto!

11 thoughts on “Pluto’s Large Moon Charon Is Stunning

  1. Nadia, could you discuss the illumination that permits these stunning images to be produced? Pluto so far from the sun that it can’t receive enough light for photography as we know it, or can it? And if it does depend upon light from the sun, that suggests the camera aperture has to be open for a while. So how can the image be so sharp when New Horizons is going 30,000 mph?

    ND: Hi, Jay! I think we may have talked about this on Twitter, but just in case: The New Horizons cameras are incredibly sensitive, so they take short exposures. Also, it isn’t as dark out there as you might think! If you look at the raw images on the JHUAPL site, they have the exposure times listed, and they’re all on the order of 100msec or so.

  2. Think about it. If there’s enough illumination for us to see it all the way from here on earth, then there’s enough illumination for a closer shot.

  3. In response to Twig: I have thought about it. That is why I’m asking Nadia. Earth-based telescopes can accumulate light over time. It is not obvious that New Horizons can do this.

  4. @Jay L. Stern Great question! I have pondered the same thing. The speed must have some kind of effect on image-taking. Of course the designers have worked it out, but I have seen the problem discussed anywhere.

    About the low illumination level: Also a good question imo, but even very low levels of light is quite easy to capture in empty space, as there is virtually no background light to outshine even a single photon bouncing of Pluto’s surface (in the visible spectrum that is).

  5. At this point in Pluto’s orbit the sun is about 400 times brighter than a full moon. You are right that at the speeds and distance it would be easy for images to get smeared if the camera wasn’t tracking its target.
    An earth based telescope may be larger than the camera on New Horizons, but in the course of gathering light over time the earth’s atmosphere puts enough distortion to destroy any detail that might be gained. The Hubble can track Pluto and take long exposures over time without atmospheric distortion, but the problem of the small size and dimness of Pluto and the distance comes into play. Hubble’s original CCD were 0.64 megapixels. New Horizon’s camera is only a 1024×1024 CCD, but it is at the end of silicon carbide telescope.

  6. Charon looks like a bigger moon to Pluto as the binary planets in the orbits in a fact. Christa D’Auria

  7. it seems that the more we find out about pluto / charon , the more inexplicable it seems to be. could i suggest that pluto may in fact a captured erstwhile drifting exoplanet. at some distant time it became caught up with a genuine KBO, and this was charon. the pair were pulled by each other into their current orbit, and could easily have ‘collected’ the other moons during the process. in the absence of any accepted hypothesis, i suggest this should be considered as a working theory.

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