What’s happening to Pluto’s atmosphere – Astronomy Magazine

New HorizonsAstronomers think they know why, thanks to the images sent back by the New Horizons spacecraft that flew past Pluto in 2015. These images revealed an unexpectedly complex surface with widely varying colors. A mysterious reddish cap at the north pole turned out to be colored by organic molecules. And a large, white, ice-covered basin called Sputnik Planitia stretched across a large part of one hemisphere.

Planetary geologists think Sputnik Planitia plays an important role in regulating Plutos atmosphere. Thats because, when it faces the sun, it releases gas into the atmosphere. Simulations suggest that this is why Plutos atmosphere has continued to grow, even as it has begun to move away from the sun.

The simulations are complicated by Sputnik Planitias color, which determines the amount of light it absorbs, and this in turn is influenced by ice formation in ways that are hard to predict.

Nevertheless, these same simulations suggest that, since 2015, Sputnik Planitia should have begun to cool, causing the atmosphere to condense into ice. Arimatsu and colleagues say thats probably whats behind their new observation.

There is a problem, however. The models suggest that Plutos atmosphere ought to have shrunk by less than 1 percent since 2016, not the 20 percent observed by the Japanese team. So there may be some other factor at work that is accelerating Plutos atmospheric collapse.

The result must also be treated with caution. The effect of Plutos atmosphere on distant starlight is small and hard to observe with the 60-centimeter reflecting telescope that the team used. They say the various sources of error in their measurement make it only marginally significant.

That means the chances to make better observations in the future will be few and far between. The team concludes with a plea for astronomers to observe Pluto with bigger, more sensitive telescopes, preferably those with diameters measured in meters.

Until then, Plutos vanishing atmosphere will remain something of a mystery.

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What's happening to Pluto's atmosphere - Astronomy Magazine