The experiments showed Europa possesses an atmosphere. Some of the flybys indicated a higher density of particles near the surface — possible plumes. For years, she had been thinking of taking another look at the data for signs of plumes, but, “there are always other things to do,” she said. “With the Hubble data in hand,” Dr. Kivelson said, “we had an idea of how big a plume might be reasonable. That we could translate into how long it would take Galileo to move across a plume that had been proposed.”

Source: New York Times May 14, 2018 15:00 UTC