In 2015 the New Horizon spacecraft passed by Pluto, and one of the images it took showed the dwarf planet had a hazy atmosphere. New data is now helping to explain how the haze around Pluto was formed. Remote observations of Pluto have been conducted by the aircraft-based Stratospheric Observatory for Infrared Astronomy or SOFIA.
Those observations show the thin haze surrounding Pluto is made of very small particles that remain in the atmosphere for prolonged periods rather than immediately falling to the surface. The data shows that the haze particles are actively replenished, which revises predictions of the fate of Pluto’s atmosphere as it moves into colder areas of space during its 248-year orbit around the sun.
Scientists on the project say that there had been hints in earlier remote observations that Pluto might have a haze around it. Still, there was no substantial evidence to confirm that it existed until SOFIA observations. Scientists say that they are now questioning if the atmosphere around Pluto will collapse in the coming years, they say that the atmosphere may be more resilient than thought.
SOFIA had been studying Pluto only two weeks before New Horizons passed by the dwarf planet in July 2015. Those observations were taken by SOFIA during an occultation, which is an eclipse-like event where Pluto casts a faint shadow on the Earth’s surface. During that event, SOFIA observed the middle layers of Pluto’s atmosphere in infrared and visible wavelengths. Those observations were combined with observations from New Horizons using radio waves and ultraviolet light to provide the most complete picture of Pluto’s atmosphere yet.
The data shows that the blue, hazy atmosphere is created as surface ice vaporizes under the distant light of the sun. The atmosphere around Pluto was mostly nitrogen gas, along with small amounts of methane and carbon monoxide. The haze particles form high in the atmosphere, more than 20 miles above the surface, as methane, and other gases react to sunlight slowly raining down on the surface of Pluto. SOFIA has shown that the particles are tiny at between 0.06 and 0.10 microns thick. The new data has scientists reevaluating predictions on the fate of Pluto’s atmosphere.