If the evidence bears out, it might represent the best evidence yet that life could exist on Saturn's biggest satellite.
Not unlike the volcanoes of Hawaii, the supposed ice volcano, known as Sotra Facula, rises 5,000 feet (1,500 meters) above the surrounding plain in a large, gently shaped dome, according to the mountain's discoverer, geophysicist Randolph Kirk.
The feature had previously been seen as a circular bright spot, nicknamed "The Rose," in radar and infrared pictures of Titan taken by NASA-ESA's Cassini probe.
But it wasn't until Cassini passed over the site a second time that scientists realized Sotra Facula is a circular mountain 40 miles (70 kilometers) across.
"Shocked" by Saturn Moon Volcano Evidence
Because the two flybys viewed the apparent ice volcano from different angles, the researchers were able to make a topographical map. Converted into a 3-D video, the combined images allowed scientists to virtually fly over the region at low altitude, as though on an airplane tour.
"I was shocked when I saw the video and suddenly realized what we were looking at," said Kirk, of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona.
The 3-D computer model also revealed at least two more giant mountains, one with another big crater. The mountains form a chain several hundred miles long, flanked by lowlands that appear to be enrobed in lava flows.
"That's a combination of features you can't make any way other than by volcanism, we believe," said Kirk, who announced the find Tuesday at a meeting of the American Geophysical Union (AGU) in San Francisco.
Planetary scientist Jeffrey Kargel agrees that a volcano is by far the best explanation.
"They have all their ducks in a row, short of having an actual sample form the surface that we could analyze," said Kargel, of the University of Arizona, Tucson, who was not part of the study team.
Ice Volcano Spews Life Onto Saturn Moon?
The presence of an ice volcano would increase the chances that Titan has the building blocks for life.
Lava from an ice volcano, the thinking goes, would contain liquid water. That water could react with chemicals called tholins—molecules produced in Titan's atmosphere when UV sunlight irradiates compounds such as methane or nitrogen.
These reactions could produce important chemical precursors to life, said planetary scientist Catherine Neish, who wasn't involved in the discovery.
In separate research also presented at the AGU meeting, Neish found that room temperature water laced with tholins will create amino acids, the building blocks of proteins, within days—much less time than it would take "cryolava" to freeze on the Saturn moon.
According to Neish, of Johns Hopkins University, "the reactions are easy and quick"—and they require temperatures only a bit above freezing.
That's important, the University of Arizona's Kargel added. "Volcanoes on Earth are destroyers of life," he said. "But on Titan, cryovolcanism would represent perhaps the very liquids that would form the habitat for life."
And if by chance there is life in warm zones in subterranean Titan, the volcanoes might carry traces of life-forms to the surface, where future explorers might someday find the frozen remnants, he added.
Cryovolcano or Asphalt Volcano?
Without physical samples of Sotra Facula, though, we can’t be absolutely sure its lava contains water.
Despite the fact that Titan is largely covered in water ice, "the presence of things that look like volcanoes doesn’t mean" they spewed watery lava, said Ralph Lorenz, a planetary scientist from Johns Hopkins University who wasn't part of the cryovolcano study.
The University of Arizona's Kargel said that, for example, the Titan volcanoes might have formed from oozing hydrocarbons such as asphalt—a not unheard-of possibility.
For one thing, Titan is believed to have lakes filled with hydrocarbons, such as liquid methane. For another, Kargel said, "we recently found asphalt volcanoes off the coast of Santa Barbara."