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Jupiter’s moon Europa could cough up water into space from small pockets in its icy crust, a new study suggests.
Europa, one of Jupiter’s four great Galilean moons, is home to a huge ocean of salt water beneath its ice shell and is widely regarded as one of the solar system’s best bets for hosting alien life.
NASA’s Hubble Space Telescope and other instruments have spotted evidence of sporadic plumes of water vapor rising perhaps 120 miles (200 kilometers) above Europa’s frigid surface. This water could come from the buried ocean, raising the exciting possibility that a spacecraft could sample this potentially viable environment without even touching the moon.
Photo: Europa, Jupiter’s mysterious icy moon
Such sampling work could be done by NASA’s Europa Clipper spacecraft, which is expected to be launched in the mid-2020s. Clipper will orbit Jupiter and study Europa during dozens of close-ups, characterizing the ocean and the ice shell and exploring possible landing sites for a future life-hunting lander. (Clipper team members pointed out that the spacecraft will likely have the good fortune to do a sampling, however, as Europa’s plume activity is not well characterized and appears to be sporadic.)
Those seemingly large plumes may have smaller cousins, which come from a source just below the surface, according to the new research.
Scientists, led by Gregor Steinbrügge of Stanford University and Joana Voigt of the University of Arizona, analyzed Europa’s Manannán Crater, a 29km-wide feature created by an impact tens of millions of years ago.
The heat generated by this impact undoubtedly melted a considerable portion of the nearby ice, and the researchers modeled what happened next. They found that a few pockets of salty liquid brine likely survived a spell after most of the melt water refrozen. In addition, the team determined that such pockets could move sideways through Europa’s shell, melting some of the adjacent ice.
Modeling work also suggested that this migration took place in Manannán: a pocket probably headed towards the center of the crater and then began to freeze, causing a build-up of pressure that eventually blew up a plume about 1 mile high. (1.6 km).
There is evidence that such a plume actually existed: a spider-like feature at Manannán that was spotted by NASA’s Galileo spacecraft, which studied the Jupiter system as it orbited the giant planet from 1995 to 2003 (the researchers entered this spider footprint in their model.)
“Although the plumes generated by the migration of the brine pockets would not provide a direct view of the ocean of Europa, our results suggest that the Europa ice shell itself is very dynamic,” Voigt said in a statement.
“The work is exciting because it supports the growing body of research that shows there may be more types of plumes on Europa,” Europa Clipper project scientist Robert Pappalardo, of NASA’s Jet Propulsion Laboratory in Southern California, said in the same statement. . “Understanding the plumes and their possible sources contributes greatly to Europa Clipper’s goal of investigating the habitability of Europa.”
The new study was published this month in the journal Geophysical Research Letters.
Mike Wall is the author of “Out There” (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
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