Ice volcanoes on Pluto suggest the dwarf planet may not be so cold after all

Pluto, once considered the ninth planet in our solar system until it was demoted to a dwarf planet in 2006had been shrouded in mystery since its discovery in 1930. But thanks to NASA’s ambitious New Horizons flyby in 2015, the curtain has been drawn and astronomers continue to reveal that Pluto is far more interesting than previously thought. .

When New Horizons flew 7,800 kilometers above Pluto’s surface, it revealed a world unlike anything we had ever seen. There were flat plains, mountains and even a thin atmosphere. It was a far cry from the stagnant, blue, icy world that had been portrayed in artists’ prints over the decades. It was a revealing discovery.

And one of the most intriguing images sent back to Earth was one that suggested the possibility of ice volcanoes, also called cryovolcanoes.

“[At the time], we recovered small pieces of images, either smaller images or parts of images first, because we couldn’t recover all the data at once. And it turns out that one of those postage stamps that we recovered contained part of this cyrovolcanic region,” said Kelsi Singer, planetary scientist at the Southwest Research Institute in Boulder, Colorado, and assistant project scientist on News Horizons.

The location of frozen water on Pluto’s surface that is a color we don’t normally associate with water or ice: red. (NASA/JHUAPL/SwRI)

These volcanoes would not look like those here on Earth. Instead, they would be fueled by water ice and other volatiles like nitrogen, methane, and carbon monoxide.

Still, there was some debate over whether the images were interpreted correctly.

More evidence of ice volcanoes

Now a new study published Tuesday in the journal Nature Communications provides more evidence to support that the frozen world is home to these strange cryovolcanoes, about seven kilometers high and about 10 to 150 kilometers wide.

“Now we have all the data. And so we can use all of this information together,” said Singer, lead author of the study. “And that includes not only images, but also typography created from images, because sometimes your eye can deceive you. So typography allows you to be honest about functionality.”

Although these cold volcanoes don’t look quite like the ones we see here on Earth, they do have some similarities.

Instead of a violent eruption with lava, rocks and dust spewing into the sky, the material produced by these volcanoes is thought to be – likely water ice, although there is also ice. Nitrogen, methane and carbon monoxide ice on Pluto – is slowly brought to the surface. by some sort of internal heating mechanism.

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Where’s the heat?

But there is still something to explain in their findings.

“Between the compositional data and the way the features are, we said there must be at least a fair amount of water ice,” Singer said of the features seen on Pluto. “And it’s hard to explain, because this hardware always has to be mobile, and it basically requires some sort of heat source.”

There are several ways to obtain this heat source. One comes from the rocky core of a moon or planet where the elements break down. This heat can remain trapped until it is somehow released.

Another is tidal warming, where a moon orbits a planet in an elliptical orbit. Due to the difference in distances, the moon can be squeezed, similar to how one might squeeze a stress ball, which in turn creates heat. This is seen in some of Saturn’s moons, such as Enceladus.

Image of Saturn’s moon Enceladus showing “tiger stripes”, long fractures from which jets of water vapor are emitted. (NASA/JPL/Institute of Space Science)

But Pluto is too far from any large body to get this tidal warming, so it could be that its relatively small core is creating this heat which then causes the mixture of water and nitrogen ice to rise. And it is likely that there are other elements at play as well.

“We think it was probably either like a very muddy mixture of ice and water. So it wasn’t like a thin flow. Or it could have been a bit like ketchup, which is, you know, not liquid, but can still flow,” Singer said.

“And we think the extrusion came from below. And if you imagine something that keeps extruding, it’s going to slowly form a dome. And then that dome is going to expand and relax, kind of like you had a ball of Silly Putty and you put it on a table: it will slowly expand and relax.”

The new study also suggests there could be an ocean 100 to 200 kilometers below Pluto’s icy crust.

“I’m not convinced it’s very common”

But not everyone is convinced that what we see on Pluto is the result of cryovolcanism.

“So yeah, there’s this topic of cryovolcanism,” said Catherine Neish, an associate professor at Western University who studies planetary surfaces, including the moons of the outer planets.

“And frankly, I’m not convinced that’s very common. Because it shouldn’t be. Think about it: you have a good glass of water. If there’s ice in it, what does ice? It floats, doesn’t it? So the water is stuck to the bottom, the ice is stuck on top, it’s really hard to get that dense water up on the less dense ice.

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But Singer thinks the data supports the idea of ​​cryovolcanism, and recent, at least in astronomical terms. She believes these eruptions may have occurred as recently as 100 million years ago. And there’s always the potential for them to happen again.

Singer said to some extent Pluto is still a bit of a mystery and there are still many questions she would like to see answered. The returned images represent about 40% of the entire dwarf planet. And seeing more of Pluto could reveal more of these regions, which would help astronomers determine how much heat might be needed to create these cryovolcanoes.

The singer says she can’t wait to tell more about this distant world. This would help astronomers better understand their own solar system and its origins, not to mention the myriads of moons that lie in the outer regions.

“Pluto is unique in its surroundings. It is unique in its distance,” Singer said. “And that’s not what we expected. So that really forces us to say, what are we missing in our models? And unfortunately, we don’t have all the answers there. “