Titan's second largest sea has mirror-like smooth surface

Radar measurements made in 2013 by NASA's Cassini spacecraft, reveal that the surface of Ligeia Mare, Titan's second largest sea, possesses a mirror-like smoothness, possibly due to a lack of winds.

"If you could look out on this sea, it would be really still. It would just be a totally glassy surface," Howard Zebker, professor of geophysics and of electrical engineering at Stanford who is the lead author of a new study detailing the research, said.

The findings also indicate that the solid terrain surrounding the sea is likely made of solid organic materials and not frozen water.

Saturn's second largest moon, Titan has a dense, planet-like atmosphere and large seas made of methane and ethane.

Measuring roughly 260 miles (420 km) by 217 miles (350 km), Ligeia Mare is larger than Lake Superior on Earth.

"Titan is the best analog that we have in the solar system to a body like the Earth because it is the only other body that we know of that has a complex cycle of solid, liquid, and gas constituents," Zebker said.

The radar measurements suggest the surface of Ligeia Mare is eerily still.

"Cassini's radar sensitivity in this experiment is one millimeter, so that means if there are waves on Ligeia Mare, they're smaller than one millimeter. That's really, really smooth," Zebker said.

One possible explanation for the sea's calmness is that no winds happened to be blowing across that region of the moon when Cassini made its flyby.

Another possibility is that a thin layer of some material is suppressing wave action.

The findings are published online in Geophysical Research Letters.