Pluto's flowing ice and mysterious red haze highlight 'a scientific wonderland'

New photos of Pluto released by Nasa reveal flows of nitrogen ice filling up craters, an atmosphere that could be on the verge of collapse, and a mysterious reddish haze extending 100 miles above the surface.

Scientists of the space agency’s historic New Horizons mission on Friday announced the discoveries with visible delight, with lead investigator Alan Stern declaring the Pluto system a “scientific wonderland”.

In a new set of high-resolution images of the dwarf planet’s surface, Stern and researcher Bill McKinnon showed evidence of nitrogen moving and spreading through a vast plain near the edge of Pluto’s large, heart-shaped region.

McKinnon pointed out “a pattern that indicates the flow of viscous ice” that appears to move “just like glacial flow on the Earth”. While water ice on Pluto freezes to the point of immovable bedrock, nitrogen and methane ice are “soft and malleable”, he said.

Swirling lines show what appears to be a world of icy movement: old craters breached and filling up with ice, mountains encrusted on the ages by the flows, and movements of ice around “what look to be barrier islands”, in McKinnon’s words.

The spacecraft’s flight past Pluto – the first time humanity has ever inspected the former planet at close range – also provided new photos from behind the dwarf planet, and revealed a haze layer in its atmosphere that astounded the scientists.

McKinnon said the team’s leading theory for the formation of the plains and flows of ice is “heat leaking out of the interior of Pluto” – an internal energy driving change on its surface. He said that there may be an internal ocean, for example, emitting heat from below the surface and nitrogen ice.

Researcher Mike Summers said the image, which shows a band of sunlight dissolving into a faint haze around Pluto, has forced scientists to “basically start from scratch” in how they think about Pluto’s atmosphere.

“This is the image that almost brought tears to the eyes of the atmospheric scientists,” Summers said, happy to have unexpected puzzles.

The haze of small particles extends to at least 100 miles above the surface, he said, five times higher than models had predicted and a profound mystery for the time being.

Summers said that the team believes the particles in this haze are responsible for Pluto’s reddish hue – that they convert into tholins, a term that encompasses a wide range of substances that have been irradiated or lost their hydrogen. The tholins however are just one piece of the puzzle, he said, “but we do know that these substances are around and the reddish color is fairly distinctive.”

Researcher Cathy Olkin said Pluto’s diverse regions and colorings could in part be explained by its long and eccentric orbit: a Plutonian year around the sun takes 248 Earth years, and its north pole is tilted to a 120-degree angle.

“Some parts are kind of baked” by sunlight, Olkin said, while others receive the tholin haze “rain” or higher or lower concentrations of methane and nitrogen, likely due to seasons.

Source: theguardian.com