ITHACA, N.Y. - Lakes of liquid methane on the surface of Titan, Saturn's largest moon, were likely formed by explosive, pressurized nitrogen just under the moon's surface, according to new research.
"Titan has very distinctive topography. Its lakes show different kinds of shapes and in some cases sharp ridges," said paper co-author Jonathan Lunine, professor of physical sciences at Cornell University.
An international team of scientists examined lakes on Titan's surface that featured steep, cratered sharp edges, raised rims and ramparts. Some of the steep ridges tower far above the moon's natural liquid sea level.
"You either need gas that ignites explosively or a gas that builds up enough pressure so that it just pops like a cork from a champagne bottle," Lunine said. "On Titan, there is nothing that will create a fiery explosion because that moon has no free oxygen. Thus, a pressurized explosion model, we argue, is a better model for those kinds of lakes. Craters are created and they fill with liquid methane."
Besides Earth, Titan is the only other body in the solar system with a stable liquid - in this case, methane - on its surface. Titan's atmosphere is filled with vaporized nitrogen.
In Titan's geophysical history, that moon has seen epochs where methane becomes depleted, leaving a nitrogen atmosphere. The nitrogen cools, producing nitrogen liquid rain in its frigid climate, which then collects in pockets under Titan's crust.
While Titan is far from the sun, a slight amount of geologic heating might occur that causes this pressurized gas to explode, popping out to the surface. In the moon's natural cycling process, liquid methane returns and fills the craters to make lakes.
Images for this research were gathered by the radar data from the NASA Cassini mission's last close flyby of Titan, just months before the spacecraft's final plunge into Saturn two years ago.