Icy Plains And Hydrocarbon Haze Spotted On Pluto

Pluto in false color. NASA.

We've had a constant stream of brand new information about Pluto in the past few weeks, and fortunately for Pluto enthusiasts everywhere, there is plenty more to come. The revelations continue with the icy plains of Pluto and its atmosphere, which we can only see when looking back at the dwarf planet towards the Sun.

Pluto is covered in a fascinating array of geological features, and some of them indicate that Pluto might have (or may have had) geologically dynamic features on its surface. Images show that a sheet of nitrogen ice flowed along the surface, and might still be flowing. Even though the ice is made of nitrogen, not water, it bears similarities to glacier movements on Earth.

“We’ve only seen surfaces like this on active worlds like Earth and Mars,” said John Spencer from the Southwest Research Institute (SwRI). “I'm really smiling.”

“At Pluto’s temperatures of -390°F (-235°C), these ices can flow like a glacier,” said Bill McKinnon of 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."

Ice flow labelled within Pluto's "heart" feature. NASA.

You might have thought that the fun was all over once New Horizons passed behind Pluto, but there's still a host of exciting discoveries to ponder over. From the back, Pluto is completely dark, nearly indistinguishable from the blackness of space. However, the Sun impressively illuminates a gorgeous haze around the planet – like a chalky smudge.

Scientists can see two separate layers of gas around Pluto: one at around 50 kilometers (30 miles) out and the other at around 80 kilometers (50 miles). In fact, the distance that the atmosphere extends surprised some scientists. The haze contains hydrocarbons, which are responsible for the dwarf planet's reddish hue.

Ghostly haze around Pluto. NASA.

Methane particles are known to exist in the atmosphere of Pluto. It is postulated that the Sun's UV rays strike these methane particles and break them up. This gives them the opportunity to reform as more complex hydrocarbon molecules. The heavier molecules sink towards the surface of Pluto, where it is colder, and condense into ice particles. 

This observation means scientists will have to return to the drawing board to figure out what is going on in the atmosphere. They originally postulated that the temperature more than 30 kilometers (20 miles) above Pluto's surface would be too warm for haze to form. 

“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 from the SwRI. “It reminds us that exploration brings us more than just incredible discoveries – it brings incredible beauty.”

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