Story highlights Bright regions on Saturn's moon Titan have been called "magic islands"

The brightness is actually due to bubbles in a "fizzing sea"

(CNN) When NASA's Cassini mission surveyed Saturn's largest moon, Titan, in 2013, scientists encountered a mystery they couldn't solve: the "magic islands."

Radar images showed unexplained bright regions in Ligeia Mare, the second largest liquid body on Titan's surface. The sea is 50% larger than our own Lake Superior and is comprised of liquid methane, ethane and nitrogen.

That environment makes the "magic islands" a less-than-ideal vacation spot. But the question remained: What are they?

Now, researchers have an answer. The bright regions that looked like islands are actually thousands of bubbles. It turns out Ligeia Mare can sometimes be an actively fizzing sea, according to a new study in Nature Astronomy . But this activity is ephemeral, which is why it has been difficult to classify and pin down.

Titan's "magic islands" aren't islands at all. They're bubbles.

"The surface looks very calm, at least in the light of RADAR observations, and from time to time we have streams of big bubbles a few centimeters in diameter reaching the surface," Daniel Cordier, the lead study author, told CNN via email. Cordier is a research scientist at the Centre National de la Recherche Scientifique in Paris.

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