Images from a retreating New Horizons reveal a rare, but distinct atmosphere on Pluto extending up to 130kms above its surface, along with flowing young glaciers on the planet.
Seven hours after its closest approach on 14 July, the probe's Long Range Reconnaissance Imager (Lorri) captured sunlight streaming through the atmosphere to reveal two hazy layers at 80kms and 50kms respectively.
Existing theories did not expect hazes above 30kms as temperatures were believed to be too hot for hydrocarbons to condense.
"My jaw was on the ground when I saw this first image of an alien atmosphere in the Kuiper Belt," said Alan Stern, principal investigator for New Horizons at the Southwest Research Institute (SwRI) in Boulder, Colorado. "It reminds us that exploration brings us more than just incredible discoveries -- it brings incredible beauty."
The hazes form when ultraviolet light breaks up methane in Pluto's atmosphere with resulting molecules going on to form more complex hydrocarbons like ethylene and acetylene.
When these hydrocarbons fall to the lower, colder parts of the atmosphere, they condense into ice particles that produce the hazes.
These are further converted to tholins that give the planet its reddish surface.
Initial analysis of the Plutonian air shows it is rare with atmospheric pressures about 10 microbars at the surface, compared to the Earth's one bar.
The Lorri images also provide evidence of exotic hydrocarbon glaciers across Pluto's surface as further proof of recent geologic activity.
A sheet of ice clearly appears to have flowed, and may still be flowing, along the Tombaugh region dubbed the "heart" of Pluto.
Data from New Horizons' Ralph instrument indicate the center of Sputnik Planum is rich in nitrogen, carbon monoxide, and methane ices.
"At Pluto's temperatures of minus-390 degrees Fahrenheit, these ices can flow like a glacier," said Bill McKinnon, deputy leader of the New Horizons Geology, Geophysics and Imaging team at Washington University in St Louis. "In the southernmost region of the heart, adjacent to the dark equatorial region, it appears that ancient, heavily-cratered terrain has been invaded by much newer icy deposits."
The New Horizons probe will continue to send data stored in its onboard recorders to Earth for more than a year. So far, hardly 4% of the data captured during the Pluto flyby has been received.
The spacecraft currently is 12.2 million kilometres beyond Pluto, flying deeper into the Kuiper Belt of icy bodies.