A Supervolcano on Pluto May Have Spewed Ice Just a Few Million Years Ago

An unusual crater on the dwarf planet hints at past volcanic activity—and a possible vast ocean beneath its surface, scientists say

A photo of Pluto
An image of Pluto taken by the New Horizons spacecraft in 2015 NASA / JPL

A crater named Kiladze on Pluto’s surface may be a supervolcano that once spewed massive amounts of icy material from the dwarf planet’s interior, according to new research.

Data gathered by the New Horizons spacecraft, which flew by Pluto in 2015, suggest that Kiladze had a period of cryovolcanic activity in the past, meaning that—rather than the molten rock, ash and gas emitted by Earthly volcanoes—it expelled ice, water and compounds like ammonia.

The findings have not yet been peer reviewed and were posted on the preprint server arXiv earlier this month.

The New Horizons mission, which launched in 2006, is currently flying through the Kuiper Belt. In the past, it transmitted data on Pluto back to Earth, which hinted at the possibility that the dwarf planet could contain a water-ice ocean beneath its surface. Imaging and spectroscopy from the spacecraft revealed signs that cryovolcanic eruptions had taken place in the past, such as icy chunks on Pluto’s surface, per New Scientist’s Alex Wilkins.

For the new study, researchers looked at New Horizons’ observations of the Kiladze crater, which is roughly 27 miles across. Its nearby surroundings seemed to be covered in water ice. Since most of Pluto’s surface is coated in ice made of methane and nitrogen, the presence of water ice indicated that Kiladze was different from the rest of the dwarf planet, Dale Cruikshank, a co-author of the study and planetary scientist at the University of Central Florida, tells Space.com’s Sharmila Kuthunur.

The water ice around Kiladze also contained ammonia, in a parallel to other sources of cryovolcanism on Pluto and elsewhere in the solar system. And water ice with ammonia is thought to lie beneath the dwarf planet’s surface, writes New Scientist.

Further, Kiladze does not appear to be similar to craters on Pluto thought to result from impacts, instead resembling sites of volcanic eruptions on Earth and Mars, per the paper.

“While Kiladze bears some resemblance to an impact crater, it is somewhat different in detail from other established impact craters on Pluto,” Cruikshank tells Newsweek’s Jess Thomson. “Its shape (slightly elongated) and the absence of a substantial central peak are both distinguishing characteristics.”

This evidence indicates the crater is a caldera—a large depression formed by the collapse of a volcano once it has spewed out material from below that previously supported its weight. The caldera’s size and the large scale of nearby water ice suggest that Kiladze is a supervolcano that has expelled more than 1,000 cubic kilometers of icy material, the study authors write.

But more research comparing Kiladze to other craters on Pluto is needed to confirm that conclusion, as David Rothery, a volcanologist at the Open University in the U.K. who was not involved in the research, tells New Scientist.

If Kiladze is a supervolcano, the researchers say its activity may have taken place within the last several million years, a time that’s relatively recent in Pluto’s 4.5-billion-year history. Their evidence comes from a constant fallout of tiny smog particles from the atmosphere, which blanket the surface in a layer of methane ice.

“Even a centimeter or two of this organic smog would mask the water ice spectral signature we observe,” Cruikshank tells Space.com. A layer that size would take just three million years to form, per the publication, so since the ice around Kiladze is not that deep, it indicates the volcanic activity happened more recently.

Volcanoes—even ones that spew ice—need heat to erupt, so recent activity would suggest Pluto’s interior has more heat than previously thought, perhaps from radioactive elements in its core. Further study of Kiladze could point to what exactly lies under the dwarf planet’s surface: an entire liquid ocean or isolated patches of water.

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