Three icy volcanoes line up on Saturn's moon Titan, giving some
of the best evidence yet that explosive eruptions are possible on
worlds beyond Earth.
The volcanic peaks and pits lie in a region called Sotra Facula
on Titan's southern hemisphere. The mountains rise more than 3,000
feet into the air, and the deepest hole sinks nearly 5,000 feet
below the surrounding plains, geologists announced in a press
conference here at the American Geophysical Union meeting on 14
"It's a combination of features that you really can't make any
way other than volcanism," said geophysicist Randolph Kirk of the
US Geological Survey. "That's what really has excited us: we
finally have some proof that Titan is an active world."
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 3D 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.
"In my opinion, Sotra Facula is the best example of a
cryovolcanic mountain on Titan and in the outer solar system,"
If the volcanic material is water-based, it could provide a
comfortable place for life to take hold, Kargel suggested.
" 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."