Astronomers See Signs of Waves on Titan’s Weird Seas

Not only are there hydrocarbon seas on Titan, a smog-shrouded moon of Saturn, but now scientists say they see the glint of waves rippling across those seas.

"If correct, this discovery represents the first sea-surface waves known outside of Earth," a research team led by the University of Idaho's Jason Barnes reported this week at the Lunar and Planetary Science Conference in The Woodlands, Texas.

Titan is the only place in the solar system besides Earth known to have liquid seas and lakes at the surface — but in Titan's case, the seas contain hydrocarbons rather than water. As viewers of this week's "Cosmos" TV episode know, Titan is so chilly that water exists only as ice, while methane and ethane regularly rain down onto the surface.

An image from the Cassini probe's Visual and Infrared Mapping Spectrometer shows the glint of sunlight reflected by hydrocarbon lakes on Titan, one of Saturn's moons. Barnes et al. / NASA / JPL / Univ. of Ariz.

The Cassini orbiter's Visual and Infrared Mapping Spectrometer spotted sunlight glinting off a sea near Titan's north pole, known as Punga Mare, in 2012 and 2013. Similar reflections have been detected before, but Barnes and his colleagues saw what they said was "unusually high flux" in the Punga Mare glint. They interpreted the flash as being caused by a reflection off rough seas.

The waves would be about an inch (2 centimeters) in height, kicked up by winds blowing at 1.7 mph (0.76 m/sec).

The researchers said they couldn't yet rule out the possibility that the strong glint was caused by mudflats covered in a liquid layer. But if it is caused by wind-driven waves, the ripples could get higher. Planetary scientists suggest that Titan's winds should pick up as northern spring takes hold.