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A tour of the solar system’s ocean worlds

The solar system is surprisingly wet.

Water is everywhere: frozen in flying chunks of space rock, floating in the atmospheres of gas giants, and — perhaps most remarkable of all — sloshing about in huge oceans hidden under the icy crusts of distant moons.

This last group includes the "ocean worlds." If there is life in our solar system (other than us, of course), there's a decent chance it lives in one of these places, and at the Woods Hole Oceanographic Institute, dozens of oceanographers and planetary scientists came together Thursday to discuss how we might explore them.

It would be a long trip — taking us to the frigid outer reaches of the solar system. But there are plenty of beaches to stop at along the way (whether you would want to go swimming in them is another matter). Here are a few of the most intriguing ocean worlds:


This moon of Jupiter has the smoothest surface of any object in the solar system; it has a thick, icy crust streaked with reddish marks thought to be deposits of salt from an interior sea. The ocean beneath that crust is kept liquid by "tidal heating" — the act of orbiting Jupiter actually keeps the moon's interior warm. And it might share some key characteristics with the oceans on Earth: a study from NASA's Jet Propulsion Lab earlier this year suggested that the moon could have the right balance of chemicals to power biological processes. A NASA mission to do several long flybys of Europa is already in the works.


In 2005, NASA's Cassini spacecraft noticed something strange going on near the surface of Enceladus, one of Saturn's moons: geyser-like jets of water vapor, carbon dioxide and other gases and particles were erupting from fissures near the moon's south pole. Beneath Enceladus's fractured surface, a liquid ocean is being churned by volcanic activity in the moon's rocky interior. Because it is thought that life on Earth first evolved around similar sea vents on our planet, this find makes the moon pretty enticing to astrobiologists. Carolyn Porco, the imaging team leader for the Cassini mission, said Thursday, "Some of us regard Enceladus is actually — with no hype — the best place in the solar system to search for extraterrestrial life."


Jupiter's biggest moon is the largest in our solar system — and the only one with its own magnetic field. Researchers have said it has a large, salty ocean sandwiched between an inner and outer layer of rock. It could even have several oceans layered between sheathes of ice, like a very strange club sandwich.


Saturn's largest moon is the only place in the solar system known to have liquid lakes on its surface (other than Earth, of course). But the far-flung satellite is super cold — a biting minus-292 degrees Fahrenheit — so they're filled with methane and ethane, rather than water (which would freeze). Below the surface, on the other hand, it's thought that a liquid ocean layer causes the moon to morph and deform as it responds to Saturn's gravitational pull. Titan has been called the most Earth-like world ever discovered, and it could theoretically be habitable.


You may laugh, but there are parts of Earth's oceans that are as foreign to scientists as any extraterrestrial sea. The first organisms around deep-sea vents weren't discovered until 1977 — before then, scientists imagined the dark, deep ocean as a lifeless place. "Of all the earthbound sciences," said Chris German, a geologist at Woods Hole who helped organize the conference, "the ocean sciences might be about as close to possible as the science of space.”

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