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Does Pluto Have an Atmosphere?

A tiny, cold rock, Pluto seems almost incapable of having an atmosphere. Between its small size and its distant location, the dwarf planet seems unlikely to have what it takes. Yet the tiny body boasts an atmosphere in a constant state of flux.

Hubble Space Telescope photo of Pluto is most detailed ever seen.
This is the most detailed view to date of the entire surface of the dwarf planet Pluto, as constructed from multiple NASA Hubble Space Telescope photographs taken from 2002 to 2003. The center disk (180 degrees) has a mysterious bright spot that is unusually rich in carbon monoxide frost. The image was released in February 2010. See the dwarf planet turn in a video based on these images.
Credit: NASA, ESA, and M. Buie (Southwest Research Institute)

Atmospheric components

The dominating gas in Pluto's atmosphere is nitrogen. Carbon monoxide and methane are also present.

Pluto boasts a rocky core covered with ices. The dwarf planet's atmosphere is affected by its temperature. The distance to Pluto from the sun varies significantly, ranging from 30 to 50 times the size of Earth's orbit because of the dwarf planet's extremely elliptical orbit. These changes in distance affect the atmosphere of the body. When Pluto lies closer to the sun, the ices thaw and a thin atmospheric layer forms. As it travels farther away, the gases re-freeze and solidify.

Pluto may have other problems. Its largest moon, Charon, is almost as massive as the dwarf planet itself, leaving many to dub it a binary system. The close proximity of the moon could allow it to draw some of Pluto's thin atmosphere its way.

Finding air

Pluto is so far away that studying anything about it is a challenge. To confirm that the dwarf planet did indeed have an atmosphere, astronomers studied it as it passed in front of bright stars over the course of its orbit. They noticed that the stars dimmed before Pluto itself moved across it, as the atmosphere of Pluto slowly blocked their light. The experiment was repeated with several stars, allowing astronomers to understand more about the air on Pluto.

Weather on Pluto

Pluto lies in the Kuiper Belt, one of millions of objects left over from the formation of the solar system. Its atmosphere resembles Neptune's moon, Triton, which boasts clouds and winds. Triton is suspected of being a captured Kuiper Belt object.

But Pluto's atmosphere is thicker than Triton's, although Neptune's moon is more massive. Scientists think that Pluto could also have clouds and winds, but observing them in detail is a challenge. When NASA's New Horizons mission arrives at the Pluto-Charon system in 2015, it will be able to provide scientists with a better understanding of the atmosphere of the icy body.

— Nola Taylor Redd, SPACE.com Contributor

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