Pluto's atmospheric haze, flowing ice like glaciers unveiled

Hazy skies and flowing "glaciers" of nitrogen ice have been discovered on Pluto.

The new discoveries were made from data collected by New Horizons spacecraft following its historic flyby of Pluto and its moons on July 14. They were unveiled during NASA's science update on the mission today.

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The hazy atmosphere was visible in a striking silhouette captured by New Horizons looking back at the night side of Pluto after the flyby.

"This is the image that almost brought tears to the eyes of the atmospheric science team," said Michael Summers, New Horizons co-investigator at George Mason University in Fairfax, Va.

That's because it reveals new surprises about Pluto's atmosphere. For one thing, it extends five times further than models predicted.

New Horizons detected layers of haze stretching 160 kilometres into the atmosphere. All this haze is believed to account for the dwarf planet's reddish colour.

Summers said the haze forms when ultraviolet light from the sun breaks apart methane gas, and the resulting compounds condense as ice particles. The haze itself interacts with sunlight to produce darker compounds.

Another surprise was visible in new closeups of a plain on Pluto's heart shaped region, Tombaugh Reggio, which show evidence of ice that flowed and may still be flowing the way glaciers flow on Earth. On Pluto, that ice is thought to be made of nitrogen rather than water.

"To see evidence of recent geological activity is just a dream come true," said William McKinnon, New Horizons co-investigator at Washington University in St. Louis.

The ice flows appear to be relatively recent: no more than a few tens of millions of years, according to McKinnon. 

Temperatures on Pluto are minus 229 degrees Celsius, and so water ice would not move anywhere in such extreme cold. But McKinnon said the nitrogen and other ices believed to be on Pluto would be geologically soft and therefore able to flow like glaciers on Earth. 

Earlier in the week, NASA released an image of a newly discovered mountain range in a heart-shaped area of Pluto called the Tombaugh region, after Pluto's discoverer Clyde Tombaugh.

The new mountain range is about one to 1.5 kilometres high, or similar in height to the Appalachian Mountains in the U.S. — making them shorter than the Rocky Mountain heights of the a different mountain range unveiled last week, NASA said.

The new image also shows a dark region in the west that is full of craters that likely accumulated over billions of years. In some places, the craters look like they're being filled by a "bright, sediment-like material."