In the search for life among other planets and solar systems, a habitable planet would exist in the “Goldilocks zone” where conditions would be just right — not too hot and not too cold. Under that definition, Jupiter’s icy moon Europa wouldn’t seem to fit the bill, but Washington University professor William McKinnon believes there are other ways for liquid water to exist on a planet covered in ice.
“Out there in deep space, it can be cold on the outside and warm on the inside. Since water is denser than ice, the ocean can hide,” he said. “Europa is in a gravitational resonance with two other moons of Jupiter, and it's continually bent back and forth. If you take a paperclip in your hand and you bend it back and forth and then touch it to your skin, the hinge, it'll be hot — and that's what's happening inside Europa.”
On Oct. 14, NASA launched the Europa Clipper spacecraft to begin a detailed study of Europa. The data the probe receives will help scientists, including McKinnon, develop a more complete understanding of the moon and may reveal whether it could sustain life.
Results from this mission could unveil “an alternative arena for the evolution of life,” he said.
McKinnon worked on three of the spacecraft’s nine instruments, including technology that hopes to see through Europa’s icy crust and measure the moon’s mass. His work also involves determining how much water is layered under the ice and the chemical composition of molecules that get chipped off Europa’s surface by things like micrometeorites.
“It's a kind of halo of stuff around Europa, and we'll be able to really buzz the surface and determine exactly what the chemical composition of the surface is,” he said. “We know there's water ice there; it's the other stuff that we're interested in — especially if any of it is organic in nature.”
Europa Clipper will fly by Mars in February for a gravitational boost and loop back around Earth in December 2026 before arriving at Jupiter in 2030.
For McKinnon, who has studied Europa for more than 40 years, the mission is a remarkable bookend of a lifelong exploration of the outer solar system.
If data turns up evidence that the moon hosts an environment suitable for life, he said, it'll be up to future generations of people to take the next step.
“The ultimate dream, of course, is to send a submersible that would actually pilot itself through the ocean, doing exploration. That's more science fiction at this point, but who knows what could be accomplished later this century.”
For more information on the Europa Clipper mission and the search for life on other planets, listen to St. Louis on the Air on Apple Podcasts, Spotify, YouTube or click the play button below.
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