By Hannah Richter , Science. Excerpt: In the late 2000s, planetary scientists scoured data gathered by NASA’s Cassini mission, a Saturn orbiter, about the planet’s mysterious icy moon Titan. Their exciting conclusion: The frozen world harbored an ocean sloshing around tens of kilometers beneath a thick ice shell. The ocean, hundreds of kilometers deep itself, might even be a cauldron for the “prebiotic” organic chemistry that led to life on Earth, they proposed. Now, nearly 2 decades later, researchers think they may have gotten the story all wrong. Research presented today here at the American Geophysical Union’s annual meeting and published in Nature claims that although Titan may have once harbored a liquid ocean, today it is frozen, except for smaller melted zones deep beneath the surface. If true, the discovery will upend the long-standing assumption that Saturn’s biggest moon is a water world, like other moons in the outer Solar System, in...