A team of planetary scientists believe they may have found a super cryovolcano on Pluto, after reviewing images and data from New Horizons' flyby of the dwarf planet in 2015.
When NASA's New Horizons probe made that visit, before going onwards to the Kuiper belt, it revealed a number of signs of volcanic episodes in the planet's history. Of particular interest to the current team, whose research is yet to be peer-reviewed, was a crater named Kiladze, which differed from its surroundings in that it contains water ice spectral properties, unlike the rest of the surface composition of primarily methane ice.
Looking at the faulted structure of the crater, its distorted shape, and collapse pits – formed as the surface sinks into a void below – the team determined that it is likely actually the caldera of a supervolcano, which could have been active in the last several million years.
While space volcanos are undeniably cool, one particularly fun type of space volcano is a cryovolcano, or ice volcano.
On other icy dwarf planets at the edge of the Solar System, similar cryovolcanoes have been found.
"Under the ice crusts, there is a layer of water, or perhaps water with something else like ammonia, and if that liquid can come to the surface, that is what we call cryovolcanism," senior research scientist at NASA’s Jet Propulsion Laboratory Dr Rosaly Lopes explained to National Geographic. "It just means cold volcanism.”
In this case, the ice and water acted as the "lava" spewing out of the volcano. Assessing the caldera and its surroundings, the team found that the volcano had spewed enough material to be classed as a supervolcano.
"In view of the size of the caldera and the large scale of the surrounding distribution of water ice, we propose that Kiladze is a 'supervolcano' in which one or more explosive events has scattered more than ~1,000 km3 [240 cubic miles] of icy cryomagma erupted from the interior onto the surface," the team wrote in their paper.
Just like on Earth, volcanoes need a heat source, which on Pluto likely comes from its core. Of particular interest was that the water ice carried the spectral signature of an ammoniated compound. Ammonia depresses the freezing point of water, meaning that it could be keeping pockets of fluid sloshing around in Pluto's interior even as the core cools down.
"We don't know if there is a subsurface global ocean of water plus various chemicals, or simply pockets of water plus chemicals left over from the time Pluto formed and had a hot interior," Planetary scientist Dale Cruikshank said in a statement. "This is a mystery for the next generation of planetary scientists to solve."
The study is published on pre-print server arXiv.