More Evidence for Europa’s Water Plumes
September 26th, 2016, 12:00PMNew observations from the Hubble Space Telescope lend even more evidence that Jupiter’s moon Europa may have water plumes shooting from the surface. Unlike Enceladus, where the Cassini spacecraft has directly observed—and flown through—the sprays from Saturn’s moon, plumes from Europa’s underground ocean are still an educated guess. Scientists explained today that they’ve been using Hubble at the limits of its capabilities to study our neighboring planet’s moons. They gathered these observations in 2014 with a technique that’s being perfected by exoplanet scientists: Hubble observed Europa as it transited Jupiter, using the bright background to better highlight any thin plumes. They also credit the Space Telescope Imaging Spectrograph, or STIS, the instrument that got a big upgrade during the last Hubble servicing mission in 2009, for having the sensitivity to collect this data. The resulting image—at right, with an image of Europa from Galileo and Voyager superimposed over the Hubble background observation—shows what may indeed be water vapor plumes coming out at the lower left. If they’re real, that means that a Europa lander could study the plumes for signs of life while it sits directly on the surface, rather than drilling down through potentially miles of ice to reach the ocean. The team noted that although Juno is in the system studying Jupiter right now, it won’t be able to help confirm the plume data because they “took great pains” to keep it as far away from Europa as possible to prevent contaminating it with any Earth-life that may have hitched a ride.