Hazy Atmosphere Reveals Pluto's Red Secret

NASA’s New Horizons spacecraft has given scientists their first hint about why Pluto has a reddish hue.

Looking back at Pluto seven hours after its historic July 14 flyby, New Horizons captured a striking view of the distant world backlit by the sun. Aesthetics aside, the image, which was released Friday, shows a surprisingly diffuse and structured layer of haze in Pluto’s atmosphere rising more than 100 miles off the surface -- five times higher than predicted by computer models.

Scientists believe methane in the atmosphere is being chemically processed by solar ultraviolet radiation, leading to the production of reddish colored hydrocarbons known as tholins that end up on Pluto’s surface.

“We think that is how Pluto’s surface got its reddish hue,” New Horizons scientist Michael Summers, with George Mason University in Fairfax, Va., told reporters during a teleconferenced press briefing.

Scientists don’t understand why Pluto’s skies are hazy and why the particles extend so far from the surface of the frozen world.

“It’s a mystery,” Summers said.

New Horizons also looked for an atmosphere on Charon, Pluto’s primary moon, but found none, a preliminary assessment shows.

“Charon has much less atmosphere than Pluto, if any. We don’t yet have the full spectral data set. We won’t have that until September,” said New Horizons lead scientist Alan Stern, with the Southwest Research Institute in Boulder, Colo.

Using radio waves blasted from NASA’s Deep Space Network, New Horizons was able to measure Pluto’s atmospheric pressure. At the surface, atmosphere pressure, which is a measure of the overall weight or mass of the atmosphere, turned out to be far less than it was just two years ago.

Pluto reached the closest point to the sun in its 248-year long orbit in 1989. Scientists suspect the atmosphere could be freezing out as Pluto careens back out into the Kuiper Belt beyond Neptune.

Newly released close-ups of Pluto’s surface showed additional signs of geologically recent activity, including nitrogen ice flows.

“You can actually see the ice going around what look to be barrier islands,” said New Horizons scientist William McKinnon, with Washington University in St. Louis.

In the northern region of Pluto’s Sputnik Planum, swirl-shaped patterns of light and dark suggest that a surface layer of exotic ices has flowed around obstacles and into depressions, much like glaciers on Earth.

The ice flows are located in a Texas-sized piece of real estate, known as Sputnik Planum and located in the western side of Pluto’s heart-shaped bright region.

“We’ve only seen surfaces like this on active worlds like Earth and Mars,” John Spencer, with the Southwest Research Institute, added in a statement.

Initial analysis of materials on the surface of Sputnik Planum show it is flush with nitrogen, carbon monoxide and methane ices.

Read more at Discovery News