Potentially Habitable Europa Has Plumes That Could Reshape Hunt for Alien Life

Jupiter's moon Europa has been regarded as one of the most interesting places in the solar system for two decades now. Scientists think its icy surface hides a vast liquid ocean and say there's a chance microbial life could be tucked away in that ocean. But the same ice shell that would protect any life below it stymies efforts to suss out what's going on.

Now, scientists may have discovered a way around that challenge. In a paper published Monday by the journal Nature Astronomy, a team presents evidence that a spacecraft has already flown through a jet of liquid rising from Europa's surface. It's hard not to dream that such a plume would carry any life up to where human instruments could study it more easily.

Conveniently, NASA is already planning to visit the moon, with a mission due to launch in the 2020s. Even before the new results were made public, a congressman used them to make the case for giving the mission additional funding.

Despite the immediate excitement about the new finding, it's actually based on old data, gathered by the Galileo spacecraft, which studied Jupiter and its moons in the 1990s and early 2000s. Scientists went back to that data after a few images taken by the Hubble Space Telescope and published over the past five years seemed to suggest something was spewing off Europa's surface.

"We really didn't pay too much attention to the location of those plumes and link that to Galileo flybys," first author Xianzhe Jia, a planetary scientist at the University of Michigan, told Newsweek. "It didn't really ring the bell."

At least, not until he was listening to a conference presentation that discussed all those papers in tandem. That's when he started to wonder whether Galileo might have accidentally flown over any of these areas and, if so, whether it had reported anything intriguing.

Related: Alien Atlantis? Extraterrestrial life may be hiding in subsurface oceans of distant planets

Jia and his colleagues found that during Galileo's closest skim over the moon's surface, in December 1997 and less than 250 miles up, the spacecraft had indeed found something strange. The magnetic field and charged particles around the moon were in upheaval in a way that suggested a plume of neutral particles spilling out into space—just the sort of signal Jia had been hoping for. Now, the hope is that Galileo's planned successor, Europa Clipper, forewarned and forearmed, will be able to confirm the plumes are there and learn more about them.

Scientists aren't quite sure yet what precisely could cause plumes on Europa. One possibility is that they're created by the huge tug of Jupiter's gravity. "That could cause some fractures on Europa to open and close during its orbit," Lynnae Quick, a geologist at the Smithsonian National Air and Space Museum who was involved in the Clipper mission but not in this paper, told Newsweek. "You may have material that's jetted into space."

Because Europa is fairly large, its own gravity wouldn't let the material spew too far, which would explain why Galileo spotted anything unusual only during its closest approach.

If the plumes are confirmed, that will make Europa the second moon in our solar system to sport such features. In 2005, scientists announced that at the south pole of Saturn's moon Enceladus, giant plumes of salty water gush out into space. That discovery rested in part on similar data about the magnetic field data, but because the Cassini spacecraft was still in the neighborhood when Enceladus's plumes were discovered, scientists could study them in much greater detail.

"They've been following in the footsteps that we laid down with Enceladus," Cassini lead imaging scientist Carolyn Porco of the Space Science Institute in Colorado, who wasn't involved in the new research, told Newsweek. "They went looking for a plume, and they found it."

Next, the team has to figure out precisely what that plume is made of, where it's coming from and if it actually suggests Europa hosts life. That's a big if, since the moon is pummeled by highly charged particles that could easily destroy living things.

NASA wants to send a spacecraft to orbit Europa, shown here with Jupiter but not to scale, sometime in the 2020s. NASA/JPL-Caltech

Even with the help of plumes, Europa may not be the easiest place to determine whether we're alone. "If you just asked right now, What is the place to go where you could return an answer as soon as possible?, you would go to Enceladus," Porco said.

But we aren't going to Enceladus next. We're going to Europa, thanks to momentum that built up before Enceladus's plumes were discovered. Fortunately, Europa Clipper will be well armed to tackle the challenge. It will be able to snap high-resolution images of the moon's surface and locate hot spots where the surface may not be frozen ice. Scientists will also be able to steer the spacecraft to try to fly through plumes and "taste" the particles in them, Quick said.

Even if Europa can't find the plumes after all, the mission should tell us plenty about this geologically exceptional moon. "The plumes would just be the icing on the cake," Quick said. "We're definitely hoping for the icing on the cake, though."