Modern media informs us the only “water world” we know of is the post-apocalyptic Earth featured in the 1995 failed blockbuster starring Kevin Costner. But a new study suggests the gas giants in our solar neighborhood might have once started out as “steam worlds,” covered in warm oceans.

Space.com reports that John Chambers, a researcher at the Carnegie Institution of Washington, has penned a paper about the way in which some protoplanets can grow, specifically focusing on the gas giants in their earliest years. According to his model, these baby planets, made of rock and “ice-rich pebbles,” clump together. Once the protoplanet reaches about 0.084 Earth masses, the fun begins.

At that point, increasing pressure melts the ice in this clump and creates a liquid, which could eventually form oceans. The liquids might then evaporate and form an atmosphere full of water vapor. All that water vapor traps in heat, driving up the world’s temperatures and turning the liquid ocean into a supercritical fluid which blurs the line between the “surface” and the actual atmosphere, Space.com reports. Chambers’ findings have been accepted for publication in The Astrophysical Journal and are now available on ArXiv.

“I calculated the structure of atmospheres in this case, and worked out when conditions are right for rapid inflow of gas to form a giant planet,” Chambers told Space.com. “The answer is, this happens when a planet is a few Earth masses, which is somewhat lower than the conventional value of 10 Earth masses.”

Obviously, much more research will need to be done in order to fully understand how the biggest planets in our solar system grew. While it’s hard to imagine Jupiter, in all its gassy glory, as anything other than a giant swirly ball, it doesn’t seem impossible. While we know that some of the gas giants have moons might currently harbor subterranean oceans — like Saturn’s moon, Enceladus, or Jupiter’s moon, Europa — we don’t know much about how watery the planets themselves could have been at one point in time.

As beautiful and chaotic as the gas giants are, it’s hard to think that billions of years ago, they were even more bonkers. Still makes a lot more sense than the plot of “Water World.”


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Photos via NASA