Images returned from the New Horizons spacecraft that sped past Pluto earlier this year have shown evidence of two possible volcanoes on the dwarf planet's surface, NASA says.
The photographs show two mountains near Pluto's south pole that are roughly circular with deep, crater-like depressions in their centers.
"These are big mountains with a large hole in their summit, and on Earth that generally means one thing—a volcano," says Oliver White, New Horizons postdoctoral researcher at NASA's Ames Research Center in Moffett Field, Calif.
If they are indeed volcanoes they're not spewing lava like volcanoes do on Earth, NASA scientists point out; they would be so-called cryovolcanoes erupting icy slush possibly containing water, ammonia, nitrogen or methane.
"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 the Ames Research Center.
The presence of possible ice volcanoes suggests an internal heat source, probably slow radioactive decay of elements created in the dwarf planet's birth 4.5 billion years ago, is keeping ice at its surface and just below warm enough to flow, researchers say.
The two mountains, named Wright Mons and Piccard Mons, tower between 2 and 3.5 miles above the surface of Pluto. Scientists say it is unclear how recently they may have been active.
The New Horizons findings have been announced in National Harbor, Md., at the 47th annual meeting of the American Astronomical Society's Division for Planetary Sciences. Visit this NASA site for more images and graphics presented at the meeting.
As the spacecraft speeds away from Pluto it continues to stream data gathered during its flyby of the dwarf planet back to Earth, a process that will take some time; only around 20 percent of its observations have been received so far.
The vast distance separating New Horizons from the Earth as it speeds toward its next target, a small icy body known as 2014 MU69, limits the bandwidths is uses for communications, researchers explain.
Still, even the limited amount of data received to date has scientists excited.
"The New Horizons mission has taken what we thought we knew about Pluto and turned it upside down," says Jim Green, director of planetary science at NASA headquarters in Washington.
Mission Principal Investigator Alan Stern of the Southwest Research Institute in Boulder, Colo., says he agrees.
"It's hard to imagine how rapidly our view of Pluto and its moons are evolving as new data stream in each week," he says. "As the discoveries pour in from those data, Pluto is becoming a star of the solar system."
