The Rapidly Changing Atmosphere of Pluto

Pluto's atmosphere has been a subject of fascination for planetary astronomers since -- well, since astronomers first discovered that it had an atmosphere in the early '90s. The interest is partly because it's fascinating that such a distant and cold world is capable of supporting an atmosphere, and partly because the presence of the atmosphere confounds all attempts to measure Pluto's size precisely. The way you determine diameters of objects that are too small to see as more than a teensy point of light is to watch the object pass in front of a star and time how long the starlight takes to wink back on again. Pluto's atmosphere bends starlight, messing up the apparent timing of that on-and-off winking, making it impossible to know for sure how big the solid part of the object is. You can try to account for this bending mathematically but only if you have a good idea of what's in the atmosphere and how dense it is.

Pluto takes 248 years to orbit the Sun. Since it was discovered in 1930 it hasn't even gone through a third of that orbit, barely more than one of its four seasons. You'd expect seasonal change on Pluto to follow the same stately pace. So it's really quite surprising to find out that Pluto's appearance has changed in the very short time that we've been studying it. I've written before on this blog about how the colors of its surface have been observed to shift over the last couple of decades. Now another team of astronomers, led by Jane Greaves, is reporting that the atmosphere has changed quite a lot over the same time scale. You can read their paper, "Discovery of carbon monoxide in the upper atmosphere of Pluto," on arXiv.…

See Planetary Society Weblog for links to further info.

Also see Space.com and physicsworld.com.