Scientists Say Titan's Second Largest Sea is Mirror Smooth

Posted on March 20, 2014

Stanford scientists say Ligeia Mare, Titan's second largest sea, has a mirror-like smoothness. Titan is Saturn's largest moon. Stanford geophysicist Howard Zebker and his team used radar measurements gathered by NASA's Cassini spacecraft to study the lake. The smoothness could be due to a lack of winds. Another explanation is that there is a thin layer of some material suppressing wave action. A false-color image of the surface of Titan made using radar measurements from Cassini is pictured above.

Zebker says in a statement, "If you could look out on this sea, it would be really still. It would just be a totally glassy surface."

Ligeia Mare is larger than Lake Superior on Earth. It measures 260 miles (420 km) by 217 miles (350 km). The lake is composed of liquid hydrocarbons, primarily liquid methane. Titan's thick cloud cover makes it difficult to see the surface with a camera, but Cassini bounced radio waves off the surface of the sea and scientists analyzed the echo.

Zebker says, "If the lake were really flat, it would act as a perfect mirror and you would have an extremely bright image of the sun. But if you ruffle up the surface of the sea, the light gets scattered in a lot of directions, and the reflection would be much dimmer. We did the same thing with radar on Titan."

Zebker says if there are waves on Ligeia Mare they are smaller than one millimeter. He says, "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."

A research paper on the surface of Ligeia Mare was published herein Geophysical Research Letters.

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CASSINI