Europa, a moon of Jupiter thought to harbor a warm, saltwater ocean sloshing beneath a thick, icy crust, has long been considered one of the best spots in the solar system to look for alien beings.
Now, citing data collected by NASA's Galileo probe more than two decades ago, scientists report that giant jets of water are spouting more than 100 miles off that moon's surface. The study, published Monday in the journal Nature Astronomy, adds to the mounting evidence that Europa is spewing its contents into space.
If the existence of the plumes is confirmed and they are linked to Europa's ocean, they could provide a tantalizingly straightforward way to sample the moon in search of signs of life. Rather than land on the surface and drill as much as 15 miles through ice – a feat that has never been achieved even on Earth – a spacecraft could simply fly through the spray and test its contents.
Researchers are already working on missions to do just that. NASA's Europa Clipper and the European Space Agency's Jupiter Icy Moons Explorer are slated to launch in the early to mid-2020s, both armed with high-resolution cameras and a suite of other sensitive instruments.
“The idea that Europa might possess plumes seems to be becoming more and more real, and that's very good news for future exploration,” said Xianzhe Jia, a space physicist at the University of Michigan and lead author of the new paper on the phenomenon.
The results of the Clipper and JUICE missions, he continued, “could have huge implications” – nudging us Earthlings closer to understanding whether we are alone.
Scientists have suspected since 2012 that Europa might harbor plumes, after the Hubble Space Telescope observed water vapor spouting above the moon's frigid south pole. Another set of observations, taken in 2014 and 2016, found a recurring jet shooting from an unusually warm “hot spot” near the moon's equator.