[LINK] Water out in the Great Beyond

[rfmcdonald]

It's fitting news that, just as Canada and the rest of the Northern Hemisphere has intensified its slide into winter, astronomers are learning more about the geologies of icy worlds in our solar system beyond our orbit.

Lisa Grossman writes in Wired Science about NASA's belief that the Cassini probe may have found water volcanoes in the Sotra Facula region on Titan.

Titan is the only body in the solar system other than Earth to have lakes, rivers, clouds, and a cycle of evaporation and mist or rainfall connecting them all. But on Titan, where temperatures hover around minus 300 degrees Fahrenheit, the flowing liquids are hydrocarbons like methane and ethane, not water.

The frigid moon is shrouded in a dense, hazy atmosphere of methane and other hydrocarbons. But astronomers think all the methane should have been broken apart by sunlight millions of years ago, suggesting that something on Titan is constantly pouring fresh methane into the atmosphere.

An icy volcano, also known as a cryovolcano, could be the methane pump scientists sought. But until now, the telltale peaks and flows indicating a volcanic eruption had been hidden.

New radar data from NASA’s Cassini spacecraft has helped astronomers build a 3-D topographical map of Sotra Facula. They saw three mountains lined up in a row. The most obvious one, which the scientists dubbed the Rose, is a single peak with a bite taken out of it and a crater 5,000 feet deep to its side. A second peak, shaped like a football stadium, lies nearby, and a third is to the north.

Measurements from Cassini’s spectrometer show evidence of some kind of magma flowing from the volcanoes to cover the surrounding planes, though what the magma is made of is still unclear. It could be a combination of water and ammonia, or it could be hydrocarbons similar to molten asphalt, candle wax or polyethylene, says planetary scientist Jeffrey Kargel of the University of Arizona, who was not involved in the new work.

[. . .]

“Volcanoes on Earth are destroyers of life,” he said. “But on Titan, cryovolcanism could represent perhaps the very liquids that would form the habitat for life, and very conveniently for us, the means by which these very speculative life forms are brought to the surface and made accessible.”

At National Geographic, meanwhile, Richard Lovett announces new models suggesting that deep subsurface oceans might exist within Pluto.

Despite its extreme cold, [Pluto] still appears to be warm enough to "easily" have a subsurface ocean, according to a new model of the rate at which radioactive heat might still warm Pluto's core.

And that ocean wouldn't be a mere puddle, noted planetary scientist Guillaume Robuchon of the University of California, Santa Cruz.

Rather, the ocean could be 100 to 170 kilometers thick beneath a 200-kilometer layer of ice, Robuchon said at an annual meeting of the American Geophysical Union in San Francisco earlier this week.

If so, Pluto would join a list of outer solar system bodies—such as Saturn's moons Titan and Enceladus—believed to possibly hold liquid water, a key ingredient for life as we know it.

Pluto's heat would come from the decay of radioactive nuclides, particularly potassium-40, in rocks deep in the dwarf planet's interior.

Even though Pluto's surface is probably colder than -230°C, there could still be plenty of liquid-preserving heat beneath the ice cap, the new model suggests.

"Ice is a good insulator," said Robuchon's collaborator, Francis Nimmo, also of the University of California, Santa Cruz.

Robuchon added that his model of Pluto's interior readily produces an under-ice ocean, as long as Pluto's core rocks contains at least a hundred parts per billion of radioactive potassium. (Earth's rocks contain approximately 0.01 percent of potassium-40.)