Two icy volcanoes may erupt at Pluto’s south pole, according to images from NASA’s New Horizons spacecraft.

The images show two mountains in circular shape and with deep depressions in their centers. One, Wright Mons, is 3 to 5 kilometres high and the other, Piccard Mons, is up to 6 kilometres high.

They look like icy volcanoes, known as cryovolcanoes, which are fueled by flowing ice, rather than hot lava.

“We’re not yet ready to announce we have found volcanic constructs at Pluto, but these sure look suspicious and we’re looking at them very closely,” says Jeff Moore, a planetary scientist at NASA’s Ames Research Center in Moffett Field, California, who is the leader of the New Horizons geology team.

If Pluto has cryovolcanoes, this suggests the volatile ices that coat its surface can flow relatively easily both at the surface and just below it, says Robert Pappalardo, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.