On stage, before a silent assembly of scientists, many of whom are experts on alien worlds, planetary scientist Paul Byrne assumed his position behind the podium. He had come to present research on Europa, a moon of Jupiter that almost certainly harbors a subsurface ocean. The moon is thought to be among the most promising places to explore for life in our solar system. But much of that promise clings to an unknown — the geologic activity of Europa’s seafloor.

“I don’t think there’s anything happening on the ocean floor,” said Byrne, of Washington University in St. Louis, to the crowd gathered at the Lunar and Planetary Science Conference on March 11.

Europa is one of three worlds in our solar system — along with Saturnian moons Enceladus and Titan — generally thought to possess the three ingredients for habitability: liquid water, energy and the chemical building blocks for life. What’s more, Europa is thought to be around 4.5 billion years old, about as old as Earth. In other words, life has had roughly the same amount of time to emerge on Europa as it has here.

As a testament to all those promising qualities, the largest spacecraft NASA has ever developed for a planetary mission, Europa Clipper, is slated for launch in October.

But as Clipper’s maiden voyage nears, it’s unclear whether the moon’s ice-covered sea can sustain life. As Byrne and other researchers question whether the seabed is dead, enigmatic quakes detected on Earth’s moon hint that mysterious mechanisms could operate within Europa, too. And even if the icy moon is uninhabitable today, it may not have always been that way.

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