In recent years, scientists have suggested that images from the Hubble telescope show plumes of icy water spewing from the surface of Jupiter’s moon Europa. Others have doubted the claim—which is fair enough, because the images are kind of fuzzy and the satellite’s instrument couldn’t always capture them.
But intrigued by Hubble’s images from 2014 and 2016, the University of Michigan’s Xianzhe Jia recently went back to the data taken by the Galileo spacecraft that flew past Europa in December 1997. Today, he and other scientists presented more evidence that the Jovian moon is spewing out big fountains of water from its icy surface. Now, the hope is that scientists can grab some of it and check for life—and in fact, NASA is already working on it.
During a three-minute datastream during the 1997 flyby, Galileo’s plasma wave instrument showed unusual emissions of charged particles. An on-board magnetometer registered a shift in the magnetic field that envelopes Europa from nearby Jupiter. To Jia, associate professor of space and planetary science at the University of Michigan, these two anomalies indicated an atmospheric disturbance very much like a geyser of salty ice water coming from a volcanic “hot spot” on the surface below. The water energized atmospheric particles, and Galileo detected their signature as it flew through.
To prove his theory, Jia and colleagues ran the data through a modeling program that compared the Galileo observations with what scientists might expect to see from a plume of the same size as imaged by Hubble. “When we tested the plume models, we found one with a good match for observations [from Galileo],” Jia said during a NASA press conference Monday to coincide with the work’s publication in Nature Astronomy.
This clever scientific detective work has boosted Europa’s fortunes as a potential home for extraterrestrial life. If a moon has liquid water spewing from its surface, maybe there’s something really interesting living below. Last year, NASA’s Cassini mission found hydrogen spewing from Saturn’s moon Enceladus, giving rise to speculation about the possibility of life-giving hydrothermal vents below its icy surface.
That’s where Charles Hibbits comes in. He’s a research scientist at Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland, and a team leader on the Europa Clipper mission that is scheduled to launch in 2020. NASA and APL are designing the spacecraft to circle Europa 44 times, swooping down just 15 miles above the frozen surface.
Hibbits is designing and building an instrument called the Mapping Imaging Spectrometer for Europa that can actually detect the plume directly, and perhaps tell whether some life form is hitching a ride. Using light signatures, MISE will also scan the moon’s surface to map the distribution of organics, salts, acid hydrates, water ice phases, and other materials that can give hints about Europa’s potential ability to support life.
Europa is covered by a crust of ice that protects an ocean below, and the plume could provide a key to understanding what lives below the surface without having land a spacecraft and drill. “The real good stuff would be down below, perhaps dormant life in the ice,” Hibbits said in an interview with WIRED. “But life requires mobility and active chemistry, and as far as we know, it requires active water. All that is in the subsurface of Europa.”
Another instrument aboard the Europa Clipper—there will be nine total—will use radar to probe through surface to look at the depth and density of the crust and the liquid water below it. If Europa Clipper detects the chemistry needed for life, or something tantalizingly close, it will make it easier to figure out where to land a future robotic mission on Europa, drill through its crust, and perhaps swim through its icy sea. That scenario played out in the 2013 sci-fi thriller “Europa Report”—though it didn’t end so well for the mission’s six human astronauts.
For his part, Hibbits is both cautious and excited about the hunt for life on Europa. “Scientists are always dubious,” Hibbits says. “We would go in hoping for the best but planning for the worst. The surprise is that it is going to be an active plume. But maybe it’s just dust.”