This image shows the evolution of a transient feature in the large hydrocarbon sea named Ligeia Mare. (credit: NASA/JPL-Caltech/ASI/Cornell)

By comparing radar images of Saturn’s exotic moon Titan, scientists have found a bright, island-like feature that has changed over time. The images, captured by the Cassini spacecraft from 2007 through 2015, show this “magic island” brightening and then dimming again.

From studying the images, scientists conclude the brightening is most likely due to waves at or beneath the surface. They do not think it’s likely to be caused by tides or sea level or seafloor changes. The surface of Titan is extremely cold, on average about -180ºC, but methane and other hydrocarbons on its surface can still exist in liquid form. The “lake” shown in this image, Ligeia, is Titan’s second-largest liquid hydrocarbon sea. With an area of about 130,000 square kilometers, it is nearly as large as the Caspian Sea, Earth’s largest lake.

Previous images indicate other, similar features exist in Kraken Mare, Titan’s largest hydrocarbon sea. With these observations, planetary scientists are beginning to understand that this moon’s oceans are not stagnant, but are instead dynamic environments. Cassini will have one more opportunity to look for “magic island” in 2017, during its final, close flyby.