Pluto Update!


Since my last post we’ve had even more exciting news about Pluto! We already know that Pluto and its system are shockingly and beautifully diverse – our first close-up image of Pluto contained these gorgeous 11,000-foot-tall mountains of water ice:

We now have a brand-new close-up image of Pluto, fitting right next to that one!

This image shows ice plains on Pluto, and while it has many interesting features, perhaps the most fascinating one is that, once again, there are NO CRATERS in this image. As Jeff Moore, Geology, Geophysics and Imaging team leader at NASA Ames said in response to the earlier image, “This is one of the youngest surfaces we’ve ever seen in the solar system.” I’ve discussed the meaning of the surface’s youth in more detail earlier, so I’ll just say here that it means this area has been resurfaced within the last 100 million years (which is not long, on a planetary timescale). This means that Pluto is geologically active, which means we have to rethink the geological processes happening inside icy worlds without big planets to give them tidal activity. However, we knew that last week. There are new features too!

This image shows guesses from the New Horizons team at what some of those new features are, although it’s important to note that this pictures does have lots of compression artifacts which will be eliminated in later data. As Moore said in Friday’s press conference, this is “not-easy-to-explain terrain” and nobody’s anywhere near sure how any of its features got there. The hills, for example, could be pushing up through the apparent cracks in the surface, or they could be emerging as the areas around them erode. The big polygons could be caused by thermal convection from heating of substances under the surface or by thermal contraction from freezing of the area. Just like with the last image release, it’s hard to say anything with any confidence until we have the rest of the data.

One thing we have learned about with a little more certainty is Pluto’s atmosphere:

This plot shows the amount of sunlight the ALICE instrument on New Horizons received as Pluto passed between it and the sun. The below animation shows how this data was taken, with ALICE receiving less and less sunlight as the light has to pass through an increasingly dense atmosphere (and no sunlight as the light can’t pass through Pluto).

From this, we know that Pluto’s atmosphere extends about 1000 miles above the surface, and spectra indicate that the atmosphere is mostly nitrogen at its top, methane lower down, and contains heavier hydrocarbons closest to the surface. However, because Pluto is not as massive as, say, Earth, and thus has weaker gravity, it’s relatively easy for that nitrogen upper atmosphere to escape: Pluto loses about 500 tons per hour of nitrogen atmosphere. In comparison, Mars only loses 1 ton per hour of atmosphere. Pluto’s loss of nitrogen is significant. As the atmosphere escapes, it is ionized and blown away by the solar wind, leaving Pluto with a tail of ionized nitrogen.

Also, Pluto has a region (marked in the below image) in the middle of Tombaugh Regio which is full of carbon monoxide. Nobody’s really sure why. There’s only one region like this that we’ve seen.

Also, this morning we got new images of two of Pluto’s five known moons, Nix and Hydra, which were only points of light to us a week ago. They weren’t even smudges – just a few bright pixels – and now they’re starting to come into focus as whole worlds of their own!


Speaking of which, as I was writing this post, a new close-up Pluto image was released! It has mountain ranges! And the interaction between the bright and dark materials on Pluto’s surface!

And craters! Plenty of craters! Since this image was just released hours ago, I haven’t found any commentary yet on how that affects the ideas about Pluto’s young surface. Perhaps Pluto’s other craters are simply covered by ice and nitrogen snow? Perhaps this area is just less geologically active? So, maybe Pluto’s surface isn’t quite as young as we thought after all…


(I find the process of discovery and exploring a brand-new never-before-seen world fascinating and exhilarating. I don’t think I’ve ever been this excited about anything in my life, so I’ll probably continue to post about Pluto. Because SPAAAAAAAAAAAAAAAAAAAAAAAAACE!)


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