Space for the day

Phil Plait has a Slate article about Pluto (no, not the Disney dog, the planet):

As the New Horizons spacecraft nears Pluto, more details are coming into view, and we are beginning to see surface features on the tiny world.
And that means we’ll see things that are... odd. Perhaps “as yet unexplained” is a better term, since we’re seeing these markings for the first time in human history. The press releases have been amazing, but the images released have been enlarged and processed in complex ways to bring out details.
But as the probe gets closer, we can see details without such means. The raw data are posted online within hours of them being transmitted back to Earth, and that means they are available for perusal.
I was looking at a pair of fresh ones taken just today, 25 June 2015, at 05:37 UTC (just after midnight, more or less, US time), when New Horizons was jus over twenty-two million kilometers from Pluto. They’re amazing. Both Pluto and its large moon Charon show all kinds of features (the only processing I did was a straight enlargement and a brightness/contrast fiddle). Overall, Charon is much darker than Pluto, but even then surface features are clearly visible.
But that bright spot on Pluto surprised me. That’s near its north pole, and it’s been seen before in earlier images, basically as a splotch. In this image it’s quite obvious.
I wondered if perhaps this was an image artifact, like a particle hit on the detector, but in fact it’s the same in the other image taken 30 seconds earlier.
The spot is very small, probably on the same scale as a single pixel or two in New Horizon’s long-range camera. That means a slight change in the pointing can make its shape look different. Remember too this image is enlarged by a factor of about ten, which can play with the shape as well. While the shape you see may not be real, the brightness contrast is.
But the important thing to note is that it’s seen in both pictures. I’ll note, too, that Pluto was in a different spot in the camera’s field of view, too, so this isn’t some bad lone pixel either, messing with the shot. This bright spot is quite real. Measuring the pixel brightnesses, it looks to be about twice as bright as the surface around it.
Right now, Pluto is only a couple of dozen pixels across in the long-range camera’s view. New Horizons is moving so rapidly that, in ten days, Pluto will be twice this size, and will double again five days after that. Features that are tantalizingly fuzzy now will continue to sharpen, and then we’ll see Pluto as it truly is.
Is this spot at the north pole a fresh impact? Is it nitrogen in its atmosphere freezing out as Pluto slowly moves away from the Sun on its elliptical orbit? Is it one big spot or a lot of little ones (like the weird ones we see on Ceres)?
Give it a couple of weeks. Because that's how close we are. After more than nine years and five billion kilometers of travel, New Horizons is about to give us quite a show.

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