Pluto Has Volcanoes But They Don’t Spew Lava

November 12, 2015 | Gillian Burrell

3D diagram of Wright Mons, a cryovolcano on Pluto's surface.
Photo credit: NASA/JHUAPL/SwRI

In the four months since New Horizons’ historic flyby of Pluto, NASA has made incredible discoveries including two cryovolcanoes.

Being demoted to a dwarf planet hasn’t hindered Pluto’s rise to fame. Ever since the spacecraft New Horizons provided us with our first glimpse of the planet, planetary scientists have been discovering that Pluto is unlike any other planet in our solar system.

From blue skies to expansive ice sheets and now cryovolcanoes, the data received from New Horizons have astounded scientists again and again. “I’d wager that for most planetary scientists, any one or two of our latest major findings on one world would be considered astounding,” commented Alan Stern, Principal Investigator at the Southwest Research Institute in Boulder, Colorado. “To have them all is simply incredible.”

SEE ALSO: Now that It's Passed Pluto, What's Next for New Horizons?

One of the surprising discoveries, announced this week by NASA, is the presence of volcanoes on the surface of Pluto. The two volcanoes, nicknamed Wright Mons and Piccard Mons, were identified when scientists generated a 3D model of Pluto’s surface by combining images from multiple angles. Because of the massive holes in each of their summits, the mountains could only be volcanoes… but they’re quite unlike earthly volcanoes.

The difference is that Pluto is mostly made of ice, not rock like Earth. So instead of spewing molten rock, Wright Mons and Piccard Mons are thought to emit a slurry of frozen water, nitrogen, ammonia, and methane. Collectively, this substance is called cryomagma, and the volcanoes are similarly called cryovolcanoes or frozen volcanoes.

Finding any sort of volcano on Pluto was completely unexpected. Given the planet’s incredible distance from the sun and its average surface temperature of -229 degrees Celsius (-380 degrees Fahrenheit), Pluto’s molten core ought to have cooled and solidified into ice long ago, but the volcanos suggest that there is still some hot liquid under Pluto’s icy shell.

This isn’t the first evidence we have that Pluto is still geologically active beneath its surface — scientists also know portions of Pluto’s surface are newer than others. For example, that distinctive heart-shaped region that received so much media attention this summer, Sputnik Planum, is completely smooth, whereas every other region of the planet is highly marked by craters. We can use the number of craters to assume that Sputnik Planum is newer than other surfaces of the planet, and it hasn’t been around long enough to be altered by comet and asteroid impacts.

Map of craters on the surface of Pluto
By counting the density of craters, planetary scientists can determine the age of a region on Pluto. Photo credit: NASA/JHUAPL/SwRI

The craters, along with the presence of volcanoes, indicate that Pluto isn’t dead inside. In order to make new surfaces, a planet’s core must seep up through the cracks to harden at the crust. So if Pluto is making new regions of crust, it must have a hot liquid core, despite the frigid temperatures out there. Crater studies like this one may help us understand how the outer planets and the Kuiper Belt were formed.

“After all, nothing like this has been seen in the deep outer solar system,” said Jeffrey Moore, New Horizons Geology, Geophysics, and Imaging team leader.

Based on materials provided by NASA.

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