Friday, July 24, 2015

New Horizons Team Finds Haze, Flowing Ice on Pluto

Annotated image of the northwestern 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. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Flowing ice and a surprising extended haze are among the newest discoveries from NASA’s New Horizons mission, which reveal distant Pluto to be an icy world of wonders. “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. “With flowing ices, exotic surface chemistry, mountain ranges, and vast haze, Pluto is showing a diversity of planetary geology that is truly thrilling."

Just seven hours after closest approach, New Horizons aimed its Long Range Reconnaissance Imager (LORRI) back at Pluto, capturing sunlight streaming through the atmosphere and revealing hazes as high as 80 miles (130 kilometers) above Pluto’s surface. A 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).

Backlit by the sun, atmospheric haze rings Pluto’s 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 was delivered to Earth on July 23.  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Backlit by the sun, atmospheric haze rings Pluto’s 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 was delivered to Earth on July 23. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

“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.”

Studying Pluto’s atmosphere provides clues as to what’s happening below.

“The hazes detected in this image are a key element in creating the complex hydrocarbon compounds that give Pluto’s surface its reddish hue,” said Michael Summers, New Horizons co-investigator at George Mason University in Fairfax, Virginia. 

Models suggest the hazes form when ultraviolet sunlight breaks up methane gas particles — a simple hydrocarbon in Pluto’s atmosphere. The breakdown of methane triggers the buildup of more complex hydrocarbon gases, such as ethylene and acetylene, which also were discovered in Pluto’s atmosphere by New Horizons. As these hydrocarbons fall to the lower, colder parts of the atmosphere, they condense into ice particles that create the hazes. 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.

“For the first time we have ground truth, measuring the surface pressure at Pluto, giving us an invaluable perspective on conditions at the surface of the planet,” said New Horizons researcher Ivan Linscott of Stanford University. “This crucial measurement may be telling us that Pluto is undergoing long-anticipated global change.”

Image of Pluto’s hazes; false-color inset reveals a variety of structures, including two distinct layers  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Image of Pluto’s hazes; false-color inset reveals a variety of structures, including two distinct layers  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The New Horizons mission also found in LORRI images evidence of exotic ices flowing across Pluto’s surface and revealing signs of recent geologic activity, something scientists hoped to find but didn’t expect. 

The new images show fascinating details within the Texas-sized plain, informally named Sputnik Planum, which lies within the western half of Pluto’s heart-shaped feature, known as Tombaugh Regio. There, a sheet of ice clearly appears to have flowed — and may still be flowing — in a manner similar to glaciers on Earth.

“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 Bill 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.”

View a simulated flyover using New Horizons’ close-approach images of Sputnik Planum and Pluto’s newly-discovered mountain range, informally named Hillary Montes, in the video here: http://go.nasa.gov/1MMEdTb

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.”

Annotated image of the southern region of Pluto’s Sputnik Planum. The large crater highlighted in the image is about 30 miles (50 kilometers) wide, approximately the size of the greater Washington, DC area.  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Annotated image of the southern region of Pluto’s Sputnik Planum. The large crater highlighted in the image is about 30 miles (50 kilometers) wide, approximately the size of the greater Washington, DC area.  Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The New Horizons mission will continue to send data stored in its onboard recorders back to Earth through late 2016. The spacecraft currently is 7.6 million miles (12.2 million kilometers) beyond Pluto, healthy and flying deeper into the Kuiper Belt.

The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA's Science Mission Directorate. SwRI, based in San Antonio, leads the science team, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA's Marshall Space Flight Center in Huntsville, Alabama.

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