Penitentes found on Pluto!

“Don’t tell Mars that my new favorite planet became Pluto!” said John Moores, assistant professor in the department of earth and space science and engineering at York University, whose findings appeared in the journal Nature in early January. But what caused Moores’ sudden change of heart?

                Interview of John Moores by York University

With help from NASA and Johns Hopkins University, Moores and a team of scientists discovered evidence of penitentes on Pluto. As Moores et al. explain in their article, “Penitentes are snow and ice features formed by erosion that, on Earth, are characterized by bowl-shaped depressions several tens of centimetres across, whose edges grade into spires up to several metres tall.”

Snow penitentes on Earth (Source: Alex Schwab/Flickr).
Snow penitentes on Earth (Source: Alex Schwab/Flickr).
Though these penitentes on Pluto are composed of frozen methane and nitrogen, not frozen water, the finding still means that snow and ice features previously only seen on Earth have been spotted elsewhere within our solar system. This suggests that these features may also exist on other similar planets.

“No matter whether we are on Earth or Pluto, the same physics applies. We can extend these results to other environments as well,” writes Moores on his blog.

Surprised by nature, they discovered snakeskin-like parallel ridges in the Tartarus Dorsa area on Pluto. These ridges resembled penitentes seen on Earth. There have been other examples of similar features on other planets, but these were often caused by processes different from the ones on Earth. Therefore, Moores et al. at first did not believe the features could actually be penitentes.

The bladed terrain of Pluto’s Tartarus Dorsa region, photographed by NASA’s New Horizons spacecraft in July 2015 (Source: NASA).
The bladed terrain of Pluto’s Tartarus Dorsa region, photographed by NASA’s New Horizons spacecraft in July 2015 (Source: NASA).
“Pluto was nothing like what we expected,” Moores notes on his blog. In order to determine that the features were true penitentes, Moores et al. applied a terrestrial model called the Claudin Model to Pluto. The model was originally developed to describe a mechanism to control the spacing of penitentes on Earth. When Moores et al. applied the model to Pluto, something strange happened: “The model, which was modified appropriately for Pluto, actually predicted penitentes consistent with what we saw on Pluto when using parameters consistent with Pluto’s extremely thin, yet extremely stable atmosphere,” Moores said.  “The theory fits the available facts quite well.” Keeping with these observations, the model also predicted that penitentes would not form at all in the more volatile nitrogen ices elsewhere on the dwarf planet, according to Moores.

First reported in the Chilean Andes by Darwin in the 1830s, penitentes form in areas of strong sunlight. In certain conditions, initial random irregularities in a snow surface can be deepened as curved depressions focus sunlight, accelerating sublimation (the transition of water molecules directly from a solid state to a gas state). As the depressions deepen, the higher points remain, shading the parts behind them, and thus slowing down sublimation. The result is a collection of spiky forms, all oriented toward the sun. Vapor processes within the depressions also contribute to the process of formation of penitentes.

How can such large penitentes form on Pluto, when Pluto’s environment is so different from the Earth? “It’s because these penitentes do not form in water ice but in methane ice, which evaporates more easily,” Moores explained to GlacierHub. “Furthermore, the atmosphere into which the sublimating methane vapor mixes is much less dense (about 15,000 times less dense than on Earth), allowing the vapor-rich layer to be thicker.”

The aligned ridges on Pluto resemble high-latitude terrestrial penitentes (source: Moores et al. / Nature).
The aligned ridges on Pluto resemble high-latitude terrestrial penitentes (source: Moores et al. / Nature).
Moores is excited about his findings. “Those 1,750 words are the most challenging I’ve ever written in my professional life,” he said, referring to his study published in Nature. “It has been an honor to be able to contribute to the science of Pluto, and I will be following the progress of the science results from New Horizons closely in the years to come.”

When asked about his future plans, Moores mentioned to GlacierHub that he hopes to continue his research on other planets. “We’re already looking at possibilities on Mars,” he said. “We’re also thinking about how we might use our simulation chambers to get a better idea of the rheology of methane at these temperatures.”


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New Findings Suggest Cryovolcanoes on Pluto

On November 9th, New Horizons mission geologists presented evidence that Pluto’s largest and most distinctive mountains might indeed be cryovolcanoes, or ice volcanoes, that are likely to have been active in Pluto’s recent geological past.

The findings are just one of over fifty new reports of exciting discoveries about Pluto, revealed just four months after the New Horizons spacecraft first encountered the dwarf planet. Geologists and astronomers presented this new research at the 47th Annual Meeting of the Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS) in National Harbor, Maryland, which began on November 9th.

Elevation maps of Pluto
Elevation maps of Pluto. Blue indicates lower terrain, green shows higher elevation, and green indicates intermediate heights. Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

New Horizons geologists presented 3-D elevation maps of Pluto’s surface, specifically of two of Pluto’s largest mountains, informally named Wright Mons and Piccard Mons.

“These are big mountains with a large hole in their summit, and on Earth that generally means one thing—a volcano,” said Oliver White, New Horizons postdoctoral researcher with NASA’s Ames Research Center, Moffett Field, California, in a New Horizons blog post.

The elevation maps suggest that these two distinctive mountains, which measure tens of miles across and several miles high, could be ice volcanoes. The research team is still tentative in its conclusions, but their current hypothesis strongly explains the geological formation of the two mountains.

White says, “If they are volcanic, then the summit depression would likely have formed via collapse as material is erupted from underneath. The strange hummocky texture of the mountain flanks may represent volcanic flows of some sort that have travelled down from the summit region and onto the plains beyond.”

The scientists don’t yet have all the explanations of their hypothesis, though. White muses, “Why they are hummocky, and what they are made of, we don’t yet know.”   

However, while Earthly volcanoes spew fiery molten rock, these cryovolcanoes are a little different: NASA scientists suspect that they would emit “a somewhat melted slurry of substances such as water ice, nitrogen, ammonia, or methane.”

If Pluto’s distinctive mountains are indeed volcanoes, the findings will provide important insight into geologic and atmospheric evolution in space.

Wright Mons
Mountain Wright Mons displays a 35-mile wide summit depression. Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

The scientific findings regarding Pluto’s geology and atmospheric systems that have emerged over the last four months have consistently continued to surprise NASA’s New Horizons mission team.

Jim Green, the director of planetary science at NASA Headquarters in Washington, commented about the mission, “The New Horizons mission has taken what we thought we knew about Pluto and turned it upside down.”

Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado, called Pluto the new “star of the solar system,” adding, “It’s hard to imagine how rapidly our view of Pluto and its moons are evolving as new data stream in each week.”

Even further, the sheer magnitude of data available for analysis have stunned scientists. Stern stated, “I’d wager that for most planetary scientists, any one or two of our latest major findings on one world would be considered astounding. To have them all is simply incredible.”

“It’s why we explore – to satisfy our innate curiosity and answer deeper questions about how we got here and what lies beyond the next horizon,” said Jim Green.





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Scientists Find Nitrogen Ice Glaciers on Pluto

Newly released close-up photographs from NASA’s New Horizons mission show evidence of exotic ice flow across dwarf-planet Pluto’s surface, indicating that Earth may not be the only planet with glacier-like geology. New Horizon’s Long-Range Reconnaissance Imager (LORRI) shows close-up photos of a sheet of ice that appears to have glided across Pluto’s surface in similar manner as glacier movement on Earth.

On Earth, melting glaciers are often characterized by surface flows around obstacles and towards the point of deepest depression, often creating swirl-shaped surfaces. New photos from the New Horizons mission show that Pluto too exhibits this characteristic warped surface.

Ice flow on the Northern region of Pluto’s Sputnik Plain
Flowing ices on Pluto, characterized by swirl-shaped patterns of light and dark. Credits: NASA.

According to Bill McKinnon, the deputy leader of New Horizons Geology, Geophysics, and Imaging team, Pluto’s frosty temperature of minus-390 degrees Fahrenheit allows these ices to move in a manner similar to those on Earth.

This movement might still be continuing, scientists speculate, but it is difficult to discern from still photographs whether Pluto’s frozen ice is still flowing.

The ice stems from the center of Sputnik Planum, a craterless plain lying in “the heart of the heart” of Pluto. According to NASA scientists, this plain, lying in the western half of the Tombaugh region, appears to be no more than 100 million years old, making it a relatively young surface of Pluto. This region is likely still be being shaped by geological processes.

NASA’s associate administrator for the Science Mission Directorate, John Grunsfeld, told NASA that the diverse and surprising findings of the New Horizons Pluto mission have been “truly thrilling.”

“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.”

Plutos Carbon Monoxide "Bulls-eye"
The carbon monoxide “bulls-eye” in the heart-shaped region of Pluto. Credits: NASA.

The ice that comprises the plain is primarily composed of nitrogen, although it is also carbon monoxide- and methane-rich. New Horizon’s Ralph Instrument reveals that the concentration of carbon monoxide in ice steadily increases towards the center of the heart’s “bulls-eye.”

These findings call into question the very definition of “glaciers,” and whether this geological term can be applied not only to other planets, but also to different chemical compositions of ice. Glaciers, as interpreted by the National Snow and Ice Data Center, are composed of fallen snow that compresses into large, thickened ice masses over a number of years. The chemical makeup of snow differs largely from Pluto’s nitrogen-, carbon monoxide-, and methane-rich ice makeup. For now, scientists and the media seem content to use the term “glacier-like” when referring to Pluto’s newly discovered nitrogen ice flow.

Through the New Horizons mission, NASA scientists have also discovered Pluto’s latitudinal planetary zones, and believe them to be caused by seasonal ice transport from the equator to the icy poles. Lending additional support to this theory, enhanced color images of the planet show that Pluto’s darkest terrains appear at the equator, while a seemingly whiter, icy expanse reigns in the northern polar region.

An enhanced color global view of Pluto.
Enhanced color global view of Pluto, taken 280,000 miles away. Credits: NASA.

Another region, the southern-most region of Pluto’s heart, Cthulhu Regio (one of the older, heavily-cratered regions of the planet) is also believed to be filled with newer icy deposits.

Plutos newfound haze
The newfound haze surrounding dwarf-planet Pluto. Credits: NASA.

The New Horizons mission has also discovered Pluto’s mountain ranges, exotic surface chemistry, and a peculiar haze surrounding the planet that extends as high as 80 miles above the planet’s surface.

Scientists and the public have been delighted with and captivated by the diverse and surprising findings of the New Horizons mission. A closer view of the distant dwarf planet has provided knowledge of Pluto’s features that are both similar to Earth’s, such as these glaciers, as well as those that are vastly different.

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Glaciers on other planets?

In light of Pluto’s newest photos from the New Horizons spacecraft mission, this Photo Friday showcases photos of the surprisingly snowy and mountainous geology of planetary bodies.

While not quite glacial, check out these photos of dwarf planet Pluto’s icy mountains and the snow-capped poles of Mars below.

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Our understanding of the composition and processes of glaciers on Earth helps scientists understand glacial-like geology in space.

Pluto’s newfound mountain ranges are estimated to be as tall as the Rocky Mountains, at around 11,000 feet. The mountains are likely composed of water-ice “bedrock.” At 100 million years old, the mountains are relatively young, at least in comparison to the age of the 4.567 billion-year-old solar system. Meanwhile, the planet Mars has two permanent ice caps that scientists have long known about. Both poles are comprised of water-ice, like Pluto’s mountains, and are occasionally covered with thick, frozen carbon dioxide.

For more information about Mars’ polar ice caps, check out this past GlacierHub article. Or instead, switch your direction of sight and see Earth’s glaciers viewed from space here.

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