Pluto has Ice Mountains, Charon is Active: New Horizons

Little Pluto, smaller than Earth’s moon, has a least one giant mountain range, with water ice the only available building material.

Little Pluto, smaller than Earth's moon, has a least one giant mountain range, with water ice the only available building material, scientists with NASA's New Horizons mission said Wednesday.

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The discovery, which popped out from the first of thousands of high-resolution images taken during New Horizons' close flyby of Pluto and its largest moon Charon on Tuesday, raised immediate questions about how the 11,000-foot (3,350 meters) mountains formed.

"We have no idea at this point," New Horizons scientist John Spencer, with the Southwest Research Institute in Boulder, Colo., told reporters.

"These mountains are quite spectacular. There may be higher ones elsewhere."

Scientists believe the mountains are made of water ice, as nitrogen, methane and other materials available on its surface aren't strong enough to support that amount of mass.

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"We are seeing the bed ice of Pluto. The water ice is strong enough at Pluto's temperatures to hold up big mountains, and that's what we think we are seeing here," Spencer said.

More details will are expected throughout the week, and especially over the next few months, as New Horizons relays back its images and science observations from its nine-day Pluto encounter.

After a journey of nearly a decade, New Horizons passed less than 7,800 miles from Pluto at 7:49 a.m. ET Tuesday. The probe is already more than 1 million miles farther into the Kuiper Belt, a region filled with ice-and-rocky bodies believed to be remnants left over from the formation of the solar system 4.6 billion years ago.

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During the eons, Pluto has not been idle. Another surprise in the New Horizons' first close-up was the complete lack of impact craters in the single frame that so far has been subject to scrutiny.

"We haven't yet found a single impact crater on this image. This means this is a very young surface because Pluto has been bombarded by objects in the Kuiper Belt and craters happen. Just eyeballing it, we think (the surface) has to be probably less than 100 million years, which is a small fraction of the 4.5 billion-year age of the solar system. It might be active right now," Spencer said.

A young surface means that Pluto has some mechanism for refreshing its face, one that requires an internal heat source. Scientists speculate that Pluto could hold a liquid ocean which gradually gives off heat as it freezes. Or it could still have radioactive materials from its formation that are releasing heat as they decay, perhaps driving ice volcanoes.

Whatever the source, the finding is significant since Pluto is the first icy world to be studied that isn't orbiting a giant planet, and therefore doesn't have tidal forces to power geologic processes.

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"This is telling us that you do not need tidal heating to power ongoing recent geological activity on icy worlds. That's a really important discovery that we just made this morning," Spencer said.

New Horizons also found that Pluto's big moon Charon is not geologically dead, defying predictions.

"Originally I thought Charon might be an ancient terrain covered in craters. Charon just blew our socks off when we had the new image today," said New Horizons deputy scientist Cathy Olkin, also with the Southwest Research Institute.

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The moon has dark and bright regions, troughs and cliffs extending 600 miles across, and a massive canyon up to six miles deep and a second canyon about half as deep.

"There is so much interesting science in this one image alone," Olkin said. "This exceeds what we came here for."

The first high-resolution image of Pluto's surface, as seen by NASA's New Horizons mission at close approach on July 14, features 11,000 ft high ice mountains.

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.