For such a small world, Pluto has an incredible diversity of features, including flowing glaciers, curiously pitted terrains, hazy skies, and multi-coloured landscapes. Now scientists from the New Horizons mission have revealed that the distant dwarf planet is even weirder than they thought, with potential ice volcanoes, floating mountains, and misbehaving moons.
Scientists presented this new set of observations from the New Horizons spacecraft, which flew past Pluto in July, on Monday at the Division for Planetary Sciences annual meeting, and the data are showing that Pluto is not what anyone expected.
Ice Volcanoes
Two pits near Pluto’s South Pole could be icy volcanic calderas. The pits are located at the summits of two enormous mountains, Wright Mons and Piccard Mons. Each mountain is a couple of miles (several kilometres) tall and at least 60 miles (100 kilometres) wide, similar in size and shape to Hawaiian shield volcanoes. But instead of fiery lava, Pluto’s volcanoes would spew ices, perhaps nitrogen, carbon monoxide, or a watery slurry dredged from a buried ocean.
Anarchic, Floating Mountains
Pluto’s mountains may be more like icebergs in the ocean than mountains on Earth. Made of water ice, these big blocks of material are probably floating on a “sea” of nitrogen ice, Moore revealed. In some regions, these mountains are as large as the Rockies but are still buoyant enough to rise high above denser nitrogen and carbon monoxide ices. “Even the largest mountains of Pluto could simply be floating,” Moore said during his presentation.
Misbehaving Moons
Pluto’s four small moons have finally been revealed, and Nix, Styx, Kerberos, and Hydra are, like most things about this system, weirder than scientists had guessed. Kerberos and Hydra look as though they’re made of two smaller objects that slowly collided and stuck together, similar to the duck-shaped comet that the Rosetta spacecraft is now orbiting. “At some point in the past, there were more than just the four [small] moons of Pluto—there were at least six,” Mark Showalter of the SETI Institute, said at a press conference.
Adding to the weirdness are the rapid rotation rates of the small moons. Hydra wins the race, spinning around itself once every 10 hours, but all the moons are pirouetting more quickly than expected. “We simply have not seen a satellite system that does this,” Showalter said. Plus, Nix has an odd, reddish crater on one face that scientists can’t fully explain yet. And Kerberos, which scientists guessed would be the dark sheep of the bunch, is actually just as bright as its three small siblings.