Europa: Ocean World

The search for life beyond Earth begins with understanding life on our home planet.

And that story, the story of life on Earth, may have begun in our oceans. And that's because, of course, if we've learned anything about life on Earth it's that where you find the liquid water you generally find life.

So what if I told you that there is an ocean out there beyond Earth? An ocean in our solar system that has been in existence for billions of years. It's an ocean that is perhaps ten times as deep as Earth's ocean. It's an ocean that is global and may contain two to three times the volume of all the liquid water on earth. It's an ocean that exists beneath the icy shell of Jupiter's moon Europa.

So how do we think we know that Europa's ocean exists? Well, it's a combination of using telescopes on the ground and having spacecraft that have flown by Europa and collected data about the surface, about the interior structure, and about the magnetic field around Europa. And a combination of those data sets leads us to a high degree of confidence that this global liquid water H2O ocean is there today and it's been there for much of the history of the solar system.

We used to think that in order for a world to be habitable you had to be at just the right distance from the sun or whatever your star was such that you could have a liquid water ocean on the surface. Now along with liquid water life as we know it needs two other key stones. The first is the building blocks for life, the stuff you find in rocks, and the second is some form of energy to help power life.

And here's where Europa is a real game changer. It is far far out from the sun and yet it's got this liquid water ocean, and the reason that Europa has liquid water is because it's orbiting Jupiter and the tidal tug and pull causes Europa to flex up and down and all that tidal energy turns into mechanical energy, which turns into friction and heat that helps maintain this liquid water ocean beneath an icy shell.

Along with helping maintain liquid water, we think that tidal energy may also allow that ocean to interact with rocks on Europa's sea floor, and it may even give rise to things like hydrothermal vents, which could help provide, not just the building blocks for life, but also the energy for life.

The question of whether or not life exists beyond Earth, the question of whether or not biology works beyond our home planet, is one of humanity's oldest and yet unanswered questions.

And for the first time in the history of humanity we have the tools and technology and capability to potentially answer this question. And, we know where to go to find it. Jupiter's ocean world Europa.

Undersea footage provided by John Delaney, University of Washington