New Horizons finds flowing ice on Pluto; NASA says mission surpassed all expectations

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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. Credits: NASA/JHUAPL/SwRI

It has been just over 10 days since New Horizons’ closest flyby of Pluto and NASA is already saying that the mission has surpassed all expectations.

The latest set of data and images sent across by New Horizons reveal Pluto as being a thrilling ice world of wonders with exotic surface chemistry, mountain ranges, and vast haze.

“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,” said John Grunsfeld, NASA’s associate administrator for the Science Mission Directorate.

NASA revealed that about seven hours after its closest flyby, New Horizons used its Long Range Reconnaissance Imager (LORRI) to capture sunlight streaming through Pluto’s atmosphere. They found hazes as high as 80 miles (130 kilometers) above Pluto’s surface and preliminary analysis of the image shows two distinct layers of haze — one about 50 miles (80 kilometers) above the surface and the other at an altitude of about 30 miles (50 kilometers).

According to Michael Summers, New Horizons co-investigator at George Mason University in Fairfax, Virginia the hazes are the key element in creation of complex hydrocarbon compounds that give Pluto’s surface its reddish hue.

Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft around midnight EDT on July 15. This global portrait of the atmosphere was captured when the spacecraft was about 1.25 million miles (2 million kilometers) from Pluto and shows structures as small as 12 miles across. The image, delivered to Earth on July 23, is displayed with north at the top of the frame. Credits: NASA/JHUAPL/SwRI
Backlit by the sun, Pluto’s atmosphere rings its silhouette like a luminous halo in this image taken by NASA’s New Horizons spacecraft around midnight EDT on July 15. This global portrait of the atmosphere was captured when the spacecraft was about 1.25 million miles (2 million kilometers) from Pluto and shows structures as small as 12 miles across. The image, delivered to Earth on July 23, is displayed with north at the top of the frame.
Credits: NASA/JHUAPL/SwRI

Based on scientific models, NASA scinetists reveal that the hazes form when ultraviolet sunlight breaks up methane gas particles in Pluto’s atmosphere. Breakdown of methane triggers formation of more complex hydrocarbon gases including ethylene and acetylene and when these hydrocarbons fall to the lower, colder parts of the atmosphere, they condense into ice particles that create the hazes.

Furter, ultraviolent sunlight chemically converts hazes into tholins, the dark hydrocarbons that color Pluto’s surface.

Scientists previously had calculated temperatures would be too warm for hazes to form at altitudes higher than 20 miles (30 kilometers) above Pluto’s surface.

“We’re going to need some new ideas to figure out what’s going on,” said Summers.

Pluto is also home to geological activity with previous proofs of such an activity evident from irregularly shaped forzen plains in Pluto’s ‘heart’. In the same location, NASA scientists have found evidence of exotic ices flowing across Pluto’s surface, which also points to signs of recent geologic activity.

“We’ve only seen surfaces like this on active worlds like Earth and Mars,” said mission co-investigator John Spencer of SwRI. “I’m really smiling.”

Additionally, new compositional data from New Horizons’ Ralph instrument indicate the center of Sputnik Planum is rich in nitrogen, carbon monoxide, and methane ices.

“At Pluto’s temperatures of minus-390 degrees Fahrenheit, these ices can flow like a glacier,” said McKinnon. deputy leader of the New Horizons Geology, Geophysics and Imaging team at 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.”

Meanwhile, New Horizons scientists are using enhanced color images (see below) to detect differences in the composition and texture of Pluto’s surface. When close-up images are combined with color data from the Ralph instrument, they paint a new and surprising portrait of Pluto in which a global pattern of zones vary by latitude. The darkest terrains appear at the equator, mid-tones are the norm at mid-latitudes, and a brighter icy expanse dominates the north polar region. The New Horizons science team is interpreting this pattern to be the result of seasonal transport of ices from equator to pole.

The newly-discovered range of mountains rises one mile (1.6 kilometers) above the surrounding plains, similar to the height of the Appalachian Mountains in the United States. These peaks have been informally named Hillary Montes (Hillary Mountains) for Sir Edmund Hillary, who first summited Mount Everest with Tenzing Norgay in 1953.

“For many years, we referred to Pluto as the Everest of planetary exploration,” said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute, Boulder, Colorado. “It’s fitting that the two climbers who first summited Earth’s highest mountain, Edmund Hillary and Tenzing Norgay, now have their names on this new Everest.”