Nonetheless, it made sense that Europa had plumes, since the Cassini spacecraft had definitely seen water plumes from Enceladus, an icy moon orbiting Saturn that's similar to Europa. "To go from there to also there are geysers coming up from that ocean, we just weren't ready for that", Kivelson says.
Today, NASA unveiled the salty plumes of Jupiter's moon Europa, but Texas Representative John Culberson beat them to it last week. For example, they may reveal Europa's ocean has the right kind of ingredients for life to thrive, they may confirm the depth of the ocean, or myriad other things.
Twice before has Nasa reported evidence, from its Hubble Space Telescope, for the existence of water plumes on Europa, though this interpretation has caused much debate. That Hubble data, however, wasn't definitive proof of erupting plumes because it's such a hard observation to make from Earth's orbit. The magnetic detectors recorded a kink in the magnetic field and the on-board plasma wave spectrometer picked up increased levels of ionized particles.
Checking for the presence of the water plumes on Europa, the Jupiter's icy moon, is, thus, of utmost significance and is getting closer to being a real thing because a United States science team managed to rebuild a 3D model of one of the plumes, basing themselves on the data collected by Galileo probe. So a team of U.S. astronomers went back and took a second look at data collected by the Galileo spacecraft during its eight-year stay in the Jovian system. "They're like a battery, combining both positive and negative to make an energy source", says Alison Murray, a biologist at the Desert Research Institute who studies organisms in extreme environments but did not take part in the research.
"I personally think that this [the new study] is strong circumstantial evidence that a plume could have been present at Europa 20 years ago, when this flyby took place", Cynthia Phillips, a NASA researcher whose work focuses on Europa, said via email.
After all, scientists have now spotted possible plume activity in the same area of Europa multiple times over a 19-year span.
"There now seem to be too many lines of evidence to dismiss plumes at Europa", said Robert Pappalardo, Europa Clipper project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena.
The only surefire way to find out if Europa does have plumes erupting from it is to send another mission there to observe and even sample the water.
When the three minutes of data associated with the plume were analyzed after the flyby in 1997, scientists thought it was a phenomenon of Jupiter's magnetic fields.
Sampling the water possibly eruption from Europa could have huge implications for our understanding of the world.
For now, researchers must wait for any further studies into the potential habitability of Europa until a water sample is collected and analyzed for its chemical properties.
But sending a robot craft to land on Europa and drill through its surface would be a much more costly and complicated endeavour than, say, flying through a plume of water ejected from the moon's innards, and measuring its composition. Not only do the plumes suggest that subsurface ocean likely exists, but it also means the Clipper, and any future mission, can just fly through the spewing mist for a sample, instead of hacking through the icy crust. "It's much more likely that any plumes would come from a water pocket or "lake" contained within the ice shell, closer to the surface", Phillips added.