Weird Pluto Mountains Are Evidence of Ice Volcanoes

Giant mountains found on Pluto are believed to be volcanoes that spewed out ice and other volatiles, new research presented on Monday shows.

NASA's New Horizons spacecraft spotted two giant mountains during its unprecedented July 14 flyby of Pluto and its primary moon Charon.

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The mountains are more akin to volcanoes found on Mars and Earth than anything ever previously found in the outer solar system, scientists said during the opening day of the American Astronomical Society's planetary sciences meeting in Maryland.

Pluto's mountains are more than 100 miles across and several miles high. The tops have depressions, similar to volcanic shapes.

"If these are indeed volcanic edifices they would form due to eruption of ice onto the surface of Pluto, rather than eruption of rock. That would be one of the most phenomenal discoveries of New Horizons and it would make Pluto and even more fascinating and unique place than it is already proving itself to be," said planetary scientist Oliver White, with NASA's Ames Research Center in Moffett Field, Calif.

"Whatever they are, they're definitely weird. Volcanoes is probably the least weird hypothesis at the moment," he added.

Heating to fire up the volcanoes likely came from the decay of naturally radioactive elements in its silicate core.

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"The heat source may have died off quite a bit over the 4.5 billion years of Pluto's existence," White said.

"We are dealing with very volatile ices at the surface, if these are indeed cryo-volcanic features, they wouldn't require as much heat to be mobilized and to erupt onto the surface as rock would for the inner terrestrial planets. While there's less heat to go around, perhaps you get more bang for your buck, given the nature of these ices," he said.

Other highlights of some 50 papers being presented by the New Horizons team include details about several large fractures cutting into Pluto's surface, possible evidence of an underground liquid ocean.

Scientists also discovered that Pluto's atmosphere is colder, smaller and more compressed than computer models predicted, and that its four small moons are spinning rapidly and wobbling.

Two of Pluto's moons, Kerberos and Hydra, appear to have two lobes and, like the comet begin studied by Europe's Rosetta spacecraft, may be the result of bodies merging together.

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"This seems to be saying to us that at some point in the past, there were more than just the four moons of Pluto – there were at least six," said New Horizons scientist Mark Showalter, with the SETI Institute in Mountain View, Calif.

The other small moons, Styx and Nix, are extremely elongated objects and could be multi-body objects as well, he added.

Hydra, Pluto's most distant moon, is the system's fastest spinner, rotating every 10 hours. That means it rotates 89 times for each of its 38-day orbits around Pluto.

Scientists expected the moons' rotations would have stabilized over time, but tidal forces from Pluto's large moon Charon are believed to keep the moons' orbits chaotic.

"There's clearly something fundamental about the dynamics of the system that we do not understand," Showalter said. "We expected chaos, but this is pandemonium."

The informally named feature Wright Mons, located south of Sputnik Planum on Pluto, is an unusual feature that's about 100 miles (160 kilometers) wide and 13,000 feet (4 kilometers) high.

After several false starts, NASA in 2001 agreed to fund an independent effort to fly a spacecraft to Pluto, the only member of the solar system’s original nine planets that hadn’t been explored. Five years later, New Horizons blasted off to begin a nearly 3 billion mile journey to Pluto, farther than any probe has traveled since the 1970s-era Pioneer and Voyager spacecraft.

Here’s a look at the New Horizons mission by the numbers.

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Launching a small spacecraft on a big rocket is one way to get going fast. Slingshotting off giant Jupiter’s gravity is another. New Horizons did both, and still the journey to distant Pluto took nearly 10 years. It is zipping along at about 31,000 mph -- fast enough to fly from New York City to Los Angeles in less than 5 minutes.

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Image: Viewed from the top of the Vehicle Assembly Building at Kennedy Space Center, NASA’s New Horizons spacecraft roars off the launch pad aboard an Atlas V rocket on Jan. 19, 2006.

At its closest approach, New Horizons will pass about 7,750 miles from Pluto and about 17,900 miles from its orbital mate Charon. The view will be about 500 times better than this image, taken on July 7 when New Horizons was just less than 5 million miles from Pluto. New Horizons will pass through the Pluto system in about 30 minutes. The probe carries seven science instruments, including LORRI, the Long Range Reconnaissance Imager, telescope.

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During the encounter, New Horizons will take hundreds of pictures in both visible and near-infrared wavelengths. The best images should depict surface features as small as 200 feet across. With nearly 3 billion miles between New Horizons and Earth, a radio signal, which travels at the speed of light, will take about 4.5 hours to reach Earth.

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Image: An artist's impression of Pluto's surface reveals an icy surface -- we're about to find out what Pluto is really made of.

With just one shot to get a close-up view of Pluto, New Horizons is designed to gather as much data as possible, as quickly as possible. In all, scientists expect the spacecraft to collect 100 times more data during closest approach than it can transmit back to Earth just after the encounter. A few high-priority images and data will be sent back just before and after closest approach, but the rest will trickle in over the next 16 months.

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Image: Diagram showing the sequence of events during New Horizons' encounter with the Pluto system.

New Horizons draws electricity from a single radioisotope thermoelectric generator, or RTG, which converts heat given off by the natural decay of about 24 pounds of radioactive plutonium. It runs on less power than a pair of 110-watt light bulbs.

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Image: Artist's impression of New Horizons flying past Jupiter, with its RTG visible in the lower right of the image.

After its Pluto flyby, New Horizons will continue out into the Kuiper Belt region of the solar system. Scientists hope to extend its mission so it can pass by at least one of the thousands of icy bodies that orbit in this vast domain. Eventually, New Horizons will end up leaving the solar system. It is expected to remain viable until the late 2030s.

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Image: Artist's impression of New Horizons encountering a Kuiper Belt object beyond Pluto.