Fifteen years after the NASA probe burned up in Jupiter's atmosphere, newly analyzed magnetic and plasma data from the mission have bolstered evidence that Europa, the planet's ice-bound moon, is likely venting water into space.
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.
Images captured by the Hubble Telescope have previously suggested the presence of ocean plumes ejected through tissues in the icy crust of Jupiter's moon. So the team reanalysed Galileo's magnetic data with modern computers and techniques, including a simulation by Zianzhe Jia, a space scientist at the University of MI, of what a plume would do to Galileo's instruments. Turns out, the team designing the probe has already planned to include a suite of instruments capable of tasting a plume, should the spacecraft fly through. Morgan Cable, an astrochemist at NASA's Jet Propulsion Laboratory, told Scientific American "up until this paper, I was very skeptical the plume existed". No other flybys picked up evidence of these eruptions, though this particular one was the closest that the spacecraft came to Europa's surface.
Xianzhe Jia, an associate professor at the University of MI who led the team that re-assessed the Galileo data, said the location, duration and variations seen in the magnetometer and plasma wave data are consistent with the presumed plume seen by Hubble. We can go back and look at that old data set anew.
"This one certainly stood out as very special", the study's lead author Xianzhe Jia said.
So why did the Galileo team miss the data during the initial flyby in 1997? But he's not the only one thrilled by the new finding.
"The result that emerged, with a simulated plume, was a match to the magnetic field and plasma signatures the team pulled from the Galileo data", NASA pointed out in the news release.
When the plume's particles become electrically conductive, they alter the surrounding magnetic fields.
Jia and his colleagues are now working on the magnetic field and plasma instruments for two future missions aimed at studying Jupiter and its moons.
"If plumes exist, and we can directly sample what's coming from the interior of Europa, then we can more easily get at whether Europa has the ingredients for life", he said in a statement.
Is there life beyond Earth?
When plumes of water spray out of Europa, the molecules are immediately battered by highly energetic particles, a process that smashes them into charged ions. "We'll surely see something we totally don't expect at Europa".
The other mission is NASA's roughly US$2 billion Europa Clipper probe, which may launch sometime between 2022 and 2025 and arrive about half a decade later. Each spacecraft would reach the mysterious world less than three years after launch. "There may be ways for material from that ocean to come out above that ice shell, and that means we'd be able to sample it". Potential passages through a plume would be a bonus, allowing both spacecraft to sniff out any signs of curious oceanic chemistry or even of life carried aloft in the tenuous vapor.
New research offers additional evidence of plumes emanating from Europa's subsurface ocean. Material jetted from a plume and snowing back down onto the moon's surface would make landing sites in close proximity to the plume the most prized spots.
Liquid water is, more or less, what NASA looks for when it decides what celestial body to explore next. It's going to happen.
NASA is designing a spacecraft called the Europa Clipper to study the moon and its environment in a bid to do just that.
He added: "If there's life at Europa, it'd nearly certainly be an independently evolved form of life".