There may be more water beneath Europa’s frozen surface than in all Earth’s oceans combined. Bob Pappalardo has spent much of his life trying to find out what happens there. Under miles of ice, far from sunlight, could this small moon of Jupiter have the conditions life needs?
I photographed Bob at the Jet Propulsion Laboratory in late 2026. Warm and easily amused, he worked in an office filled with artifacts and Star Trek memorabilia. The Europa Clipper team had its own offices and control room. It reminded me of a startup, a group of people gathered around an idea they were determined to make happen. Their spacecraft’s destination happened to be Jupiter.
As a boy, Bob hung handmade planets from his bedroom ceiling, their moons fashioned from masking tape and toothpicks. At Cornell, Carl Sagan allowed him to sit in on a graduate seminar called Ices and Oceans in the Outer Solar System. He discovered that studying the geology of other worlds could be a profession.
Ice became a particular fascination. On a planetary scale, it bends, fractures, and flows, preserving clues to forces beneath the surface. After doctoral work at Arizona State University, Bob helped plan observations of Jupiter’s icy moons for NASA’s Galileo spacecraft.
Europa’s surface was extraordinary. Ridges stretched across it, and pieces of crust appeared to have broken apart and rotated. Its scarcity of large impact craters suggested that older terrain had been replaced. Together with magnetic measurements, these observations provided strong evidence for an ocean beneath the ice.
Jupiter helps keep that ocean liquid. As Europa travels along its slightly elongated orbit, changing gravitational forces flex its interior, generating heat. At the ocean floor, water interacting with rock could supply chemical energy for life. On Earth, organisms thrive in places sunlight never reaches. Could something similar happen on Europa?
In 2006, Bob left academia for JPL to help turn a proposed Europa mission into a real spacecraft. He gave himself three years. Nine passed before NASA approved the mission that became Europa Clipper.
As project scientist, he helped shape its scientific goals and bring scientists and engineers together to achieve them. Clipper launched in October 2024. Its mission calls for arrival at Jupiter in 2030 and 49 close passes of Europa, investigating the ice, ocean, and chemistry. It will assess whether the moon has environments that could support life. Detecting life itself would require a different mission.
Later, we visited JPL’s museum. Bob showed me full size models of spacecraft he had worked on, then stepped behind the guardrails to touch them. That was the moment that stayed with me. After all the talk of distant oceans and the engineering needed to reach them, here was something familiar and deeply human. He touched them with a father’s affection.
