This week, I got into one of the more intriguing aspects of astrobiology – the search for life in the cosmos! Right now, all of our astrobiology efforts are focused on Mars, the most “habitable” planet (by our standards) beyond Earth. But what of the icy moons that orbit Jupiter, Saturn, and beyond? For decades, scientists have speculated that moons orbiting gas giants beyond the “Frost Line” could have warm-water oceans that could support life.

These oceans result from the gravitational pull of the gas giants they orbit, causing tidal flexing in their interiors. This, it was theorized, would lead to hydrothermal activity at the core-mantle boundary, where the icy outer shell meets the rocky and metallic core. The energy this released would maintain a liquid-water ocean rich in the chemical elements we associate with life.

The theory emerged by the 1970s after scientists got a good look at some of Jupiter’s largest moons – Europa and Ganymede – which showed evidence of resurfacing, plume activity, and their interactions with Jupiter”s magnetic field. In recent years, the list of “Ocean Worlds” has expanded to include moons like Titan, Enceladus, Dione, Ariel, Umbriel, Titania, Oberon, Triton, Charon, and even Pluto!

In all cases, these bodies have geological activity or sufficient nuclear elements (which decay to produce heat) to maintain liquid water in their interiors. The plethora of “Ocean Worlds” in our Solar System also has implications for the search for life in extrasolar systems. After all, if icy satellites in our outer Solar System could support life, then similar bodies are sure to exist out there (in abundance). Check it out below!

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