Pluto's Blue Atmosphere in the Infrared

Explanation: The blue ring around Pluto is caused by sunlight scattering from haze particles common in Pluto's atmosphere; scientists believe the haze is a photochemical smog resulting from the action of sunlight on methane and other molecules, producing a complex mixture of hydrocarbons such as acetylene and ethylene. These hydrocarbons accumulate into small particles — a fraction of a micrometer in size — which scatter sunlight to make the blue haze. The new infrared image, when combined with earlier images made at shorter, visible wavelengths, gives scientists new clues into the size distribution of the particles. The whitish patches around Pluto's limb in this image are sunlight bouncing off more reflective or smoother areas on Pluto's surface — with the largest patch being the western section of the informally named Cthulhu Regio. Future LEISA observations returned to Earth should capture the remainder of the haze, missing from the lower section of the image.

Pluto

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute