Liquid amid the gas giants

When we think of oceans, our minds usually drift to Earth's blue expanses—vast, mysterious, and teeming with life.

- HRITHIK KIRAN BAGADE

Oceans have shaped our climate, sculpted continents, and served as the cradle of evolution. Yet, as our robotic explorers travel deeper into the Solar System, we have come to realize that oceans may not be exclusive to Earth. In fact, the Solar System appears to be far wetter than we ever imagined, though many of these oceans are hidden beneath layers of ice, buried in darkness, or composed of strange chemicals. These alien oceans may hold secrets not only about the formation of planets and moons, but also about life itself.

The search for extraterrestrial oceans begins with our own watery world. Earth is, so far, the only planet we know of where oceans exist on the surface, supporting a vast diversity of life. But Earth is also our point of reference, the standard by which we measure habitability elsewhere. Water, in liquid form, is essential for life as we know it. The question that drives much of planetary exploration is simple: Where else could liquid water exist?