November 25, 2017

Haunting sunset vista shows foggy hazes on Pluto

Just 15 minutes after its closest approach to Pluto on July 14, 2015, NASA's New Horizons spacecraft looked back toward the sun and captured this near-sunset view of the rugged, icy mountains and flat ice plains extending to Pluto's horizon. The smooth expanse of the informally named icy plain Sputnik Planum (right) is flanked to the west (left) by rugged mountains up to 11,000 feet (3,500 meters) high, including the informally named Norgay Montes in the foreground and Hillary Montes on the skyline. To the right, east of Sputnik, rougher terrain is cut by apparent glaciers. The backlighting highlights more than a dozen layers of haze in Pluto’s tenuous but distended atmosphere. The image was taken from a distance of 11,000 miles (18,000 kilometers) to Pluto; the scene is 780 miles (1,250 kilometers) wide. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Just 15 minutes after its closest approach to Pluto on July 14, 2015, NASA’s New Horizons spacecraft looked back toward the sun and captured this near-sunset view of the rugged, icy mountains and flat ice plains extending to Pluto’s horizon. The smooth expanse of the informally named icy plain Sputnik Planum (right) is flanked to the west (left) by rugged mountains up to 11,000 feet (3,500 meters) high, including the informally named Norgay Montes in the foreground and Hillary Montes on the skyline. To the right, east of Sputnik, rougher terrain is cut by apparent glaciers. The backlighting highlights more than a dozen layers of haze in Pluto’s tenuous but distended atmosphere. The image was taken from a distance of 11,000 miles (18,000 kilometers) to Pluto; the scene is 780 miles (1,250 kilometers) wide. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

A crescent Pluto stars in pictures captured just after NASA’s New Horizons spacecraft’s July flyby of the distant dwarf planet, exposing eerie backlit fog banks and glacial flows that scientists say hint at an Earth-like weather cycle.

But instead of Earth’s water-driven hydrological cycle, Pluto has soft, exotic ices like nitrogen that scientists believe might flow across the surface like glaciers and sublimate into a gaseous state to form haze layers in the frozen world’s thin atmosphere.

“In addition to being visually stunning, these low-lying hazes hint at the weather changing from day to day on Pluto, just like it does here on Earth,” said Will Gundy, the New Horizons composition team lead from Lowell Observatory in Flagstaff, Arizona.

The latest view of Pluto released by NASA on Thursday was captured about 15 minutes after New Horizons made its closest approach July 14. The spacecraft beamed the image from New Horizons’ Ralph instrument’s wide-angle camera Sept. 13.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Huge mountains likely composed of water ice tower above Pluto’s surface in the picture, which reveals stunning topographic relief on the icy world’s rugged landscape.

“This image really makes you feel you are there, at Pluto, surveying the landscape for yourself,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute in Boulder, Colorado. “But this image is also a scientific bonanza, revealing new details about Pluto’s atmosphere, mountains, glaciers and plains.”

New Horizons is still sending back images from its July 14 encounter with Pluto. The probe is flying more than 3 billion miles from Earth, and its communications link only allows data to stream back to the ground at about 2 kilobits per second, much slower than a dial-up Internet connection.

“The image shows more than a dozen thin haze layers extending from near the ground to at least 60 miles (100 kilometers) above the surface,” officials wrote in a NASA press release. “In addition, the image reveals at least one bank of fog-like, low-lying haze illuminated by the setting sun against Pluto’s dark side, raked by shadows from nearby mountains.”

The wide-angle view covers a scene 780 miles (1,250 kilometers) across, according to NASA.

n this small section of the larger crescent image of Pluto, taken by NASA's New Horizons just 15 minutes after the spacecraft's closest approach on July 14, 2015, the setting sun illuminates a fog or near-surface haze, which is cut by the parallel shadows of many local hills and small mountains. The image was taken from a distance of 11,000 miles (18,000 kilometers), and the width of the image is 115 miles (185 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
In this small section of the larger crescent image of Pluto, taken by NASA’s New Horizons just 15 minutes after the spacecraft’s closest approach on July 14, 2015, the setting sun illuminates a fog or near-surface haze, which is cut by the parallel shadows of many local hills and small mountains. The image was taken from a distance of 11,000 miles (18,000 kilometers), and the width of the image is 115 miles (185 kilometers). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The vast icy plain scientists have informally named Sputnik Planum appears in the image captured by the Ralph instrument. Geologists think nitrogen vapors — and perhaps frozen methane or carbon monoxide — from Sputnik Planum may be lofted into Pluto’s atmosphere to rain down elsewhere on the dwarf planet.

Sputnik Planum makes up the western lobe of Pluto’s bright heart-shaped region discovered by New Horizons. The eastern lobe appears to be made of a different material, and scientists believe it may be the dumping ground for molecules that evaporate from Sputnik Planum.

The new image from the Ralph camera also shows glaciers flowing back into Sputnik Planum from the blanketed region to the east, according to NASA.

Ice (probably frozen nitrogen) that appears to have accumulated on the uplands on the right side of this 390-mile (630-kilometer) wide image is draining from Pluto's mountains onto the informally named Sputnik Planum through the 2- to 5-mile (3- to 8- kilometer) wide valleys indicated by the red arrows. The flow front of the ice moving into Sputnik Planum is outlined by the blue arrows. The origin of the ridges and pits on the right side of the image remains uncertain. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Ice (probably frozen nitrogen) that appears to have accumulated on the uplands on the right side of this 390-mile (630-kilometer) wide image is draining from Pluto’s mountains onto the informally named Sputnik Planum through the 2- to 5-mile (3- to 8- kilometer) wide valleys indicated by the red arrows. The flow front of the ice moving into Sputnik Planum is outlined by the blue arrows. The origin of the ridges and pits on the right side of the image remains uncertain. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The flows have analogs on Earth, scientists said. They appear similar to features identified on the edges of ice caps on Greenland and Antarctica.

“We did not expect to find hints of a nitrogen-based glacial cycle on Pluto operating in the frigid conditions of the outer solar system,” said Alan Howard, a member of the mission’s geology, geophysics and imaging team from the University of Virginia, Charlottesville. “Driven by dim sunlight, this would be directly comparable to the hydrological cycle that feeds ice caps on Earth, where water is evaporated from the oceans, falls as snow, and returns to the seas through glacial flow.”

“Pluto is surprisingly Earth-like in this regard, and no one predicted it,” Stern said.

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