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New Horizons' Results: Flowing Ice, Haze, and Mysterious Plains on Pluto

Jul 25, 2015 11:27 PM EDT
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A little more than a week after the intrepid New Horizons made its brief but historic rendezvous with our solar system's favorite dwarf planet, NASA is already revealing some stunning images and data from Pluto's surface. Now, NASA experts are saying that the protoplanet is more exciting and more mysterious than they ever expected.

"We knew that a mission to Pluto would bring some surprises, and now -- 10 days after closest approach -- we can say that our expectation has been more than surpassed," John Grunsfeld, NASA's associate administrator for the Science Mission Directorate, said in a statement on Friday (July 24). "With flowing ices, exotic surface chemistry, mountain ranges, and vast haze, Pluto is showing a diversity of planetary geology that is truly thrilling."

The Highest Haze

Interestingly, one of the most stunning images captured by New Horizons was not taken when the spacecraft was closest to Pluto. Instead, the below photo was taken seven hours after the fly-by, when New Horizons aimed its Long Range Reconnaissance Imager (LORRI) back at Pluto, capturing sunlight streaming through the atmosphere. This silhouetted shot revealed stunning hazes ringing the terrestrial world that reach up to 80 miles high (130 km). (Scroll to read on...)

(Photo : NASA/JHUAPL/SwRI) This global portrait of the atmosphere was captured by New Horizons when the spacecraft was about 1.25 million miles (2 million km) from Pluto and shows structures as small as 12 miles across. Photo time: ~12:00 EDT on July 15. Delivered to Earth on July 23.

"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."

Of course, this discovery has a great deal of scientific merit as well. A hasty analysis based on data collected by New Horizons' impressive suite of scientific instruments helped the researchers determine that this haze gives the protoplanet its distinctive blush.

"The hazes detected in this image are a key element in creating the complex hydrocarbon compounds that give Pluto's surface its reddish hue," New Horizons co-investigator Michael Summers, of George Mason University, explained.

He added that they so-far know that a complex interaction between ultraviolet light and methane gas in Pluto's atmosphere gives rise to the haze, but the specifics remain... hazy. (Scroll to read on.)

( Credit : NASA/JHUAPL/SwRI ) New Horizons' Alice instrument counts decreases in light intensity as Pluto's atmosphere passes in front of the Sun. The decreasing count rate is due to UV sunlight having to pass through progressively larger amounts of the atmosphere as the spacecraft line of sight gets closer to Pluto. Data will help experts determine the hazy atmophere's composition.

For instance, the scientists had predicted that it would be too warm for icy hazes to form at altitudes higher than 20 miles (30 kilometers) above Pluto's surface, and yet, there they are.

"We're going to need some new ideas to figure out what's going on," said Summers.

Pluto's Great Plain

Still, Pluto's Haze wasn't the only tantalizing mystery that New Horizons' investigators are drooling over. Just north of Pluto's icy mountains, there is a great plain lacking all the rugged geographical features that characterize the rest of the alien world. Located in a 'heart feature' named "Tombaugh Regio" - after Clyde Tombaugh, who discovered Pluto in 1930 - the plain appears to be no more than 100 million years old - relatively young when considering the age of our solar system (~5 billion years).

"This terrain is not easy to explain," Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) said in a statement. "The discovery of vast, craterless, very young plains on Pluto exceeds all pre-flyby expectations." (Scroll to read on...)

(Photo : NASA/JHUAPL/SWRI) Heart of the heart: The surface appears to be divided into irregularly-shaped segments that are ringed by narrow troughs. Features that appear to be groups of mounds and fields of small pits are also visible. Image was acquired by the LORRI on July 14 from a distance of 48,000 miles (77,000 km). Features as small as one-half mile (1 km) across are visible.

Images acquired when New Horizons was are mere 48,000 miles (77,000 kilometers) from the dwarf planet's surface showed that this mysterious icy region, informally named "Sputnik Planum," resembles a field of frozen and cracked mud. This could indicate that the region is still geologically active.

"We've only seen surfaces like this on active worlds like Earth and Mars," mission co-investigator John Spencer of SwRI added. "I'm really smiling."

Icy 'Rivers' Running

What's more, these initial images hint that the icy plain might be spotted with ongoing ice-flows.

"At Pluto's temperatures of minus-390 degrees Fahrenheit, these ices can flow like a glacier," Bill McKinnon, deputy leader of the New Horizons GGI, explained. "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." (Scroll to read on...)

(Photo : NASA/JHUAPL/SwRI) Scientific interpretation of swirl-shaped patterns of light and dark, exotic ices on Pluto's surface. Click for original image unannotated.

This could explain the uncharacteristically smooth nature of the Sputnik Planum, but it's a theory that can only be confirmed after higher-resolution and stereo images from New Horizons' digital recorders get into the hands of GGI scientists. This crucial information is due to be sent back to Earth for review sometime early next year.

"With the flyby in the rearview mirror, a decade-long journey to Pluto is over --but, the science payoff is only beginning," said Jim Green, director of Planetary Science at NASA Headquarters in Washington. "Data from New Horizons will continue to fuel discovery for years to come."

"We've only scratched the surface of our Pluto exploration," Stern added, "but it already seems clear to me that in the initial reconnaissance of the solar system, the best was saved for last."

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

 - follow Brian on Twitter @BS_ButNoBS

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