Europa may – Signs of water plumes from Jupiter’s moon Europa—once suggested by hydrogen and oxygen signals near the south pole—have failed to hold up under a fresh review of nearly a decade of Hubble Space Telescope observations. The disappearance of the ultraviolet “plum
For more than a decade, Europa’s south pole has carried a tantalizing promise: that the moon’s thick ice shell might sometimes crack open, letting water escape into space.
In 2013, Lorenz Roth and colleagues reported excess ultraviolet light tied to hydrogen and oxygen atoms hovering around Europa’s south pole. The interpretation at the time was bold—cracks in Europa’s icy surface appeared to open intermittently, releasing water from the moon’s inner ocean.
That idea has never been just a curiosity. Europa’s ocean is widely viewed as one of the best places to look for life in the solar system. The trouble is that the ice shell is kilometers thick, making it extremely difficult to study directly. Plumes—if they exist—could offer a different route: a spacecraft might be able to collect material simply by flying through the expelled gas and vapor. without landing or drilling.
But the plume story has now changed.
Roth. a planetary astronomer at KTH Royal Institute of Technology in Stockholm. and his team revisited Europa using nearly a decade of observations from the Hubble Space Telescope. Their new analysis. reported in May in Astronomy & Astrophysics. finds no strong evidence for the vapor jets that were claimed 13 years ago.
“They disappeared,” Roth says. “I don’t think there’s any strong evidence left.”
The investigation began with a question that feels almost mechanical—until it didn’t turn out that way. Roth describes returning to Hubble after the 2013 result with the confidence that the signals would recur. “I thought, we know where and when it is now, we’ll see it again,” Roth says. “And we didn’t.”.
The pattern emerged across new and old datasets. In the latest study, Roth and colleagues analyzed 20 Hubble observations taken from 2013 to 2020. They also included three additional observations—two from 2012 and one from 1999—that had been used in the original 2013 work.
Europa, at least in ultraviolet light, is not an easy target. Even Hubble’s sharp view renders Europa as a fuzzy ball of TV static. Still, the team examined spectral data for evidence that hydrogen and oxygen were being released near the moon’s south pole.
In the original claim, Jupiter’s moon Europa showed extra hydrogen emanating from its south pole in the spectral data. But further observations showed no sign of the excess.
This time, the disappearance is the central finding. The new analysis reports that the ultraviolet excess disappeared.
Part of the change comes from better measurement of Europa’s position in Hubble’s field. Roth and colleagues say the new study used improved methods for constraining where Europa’s edges are—because being off by only a pixel or two can alter the result.
The study also reflects what has been learned about Europa over the years. The team incorporated knowledge from the last 13 years, including the fact that Europa has an extensive hydrogen exosphere that Hubble can detect.
That matters because it offers an alternative explanation for the kinds of hydrogen signals that initially looked like plume activity.
What’s not ruled out is the bigger question—whether any plume activity could still be happening at levels too faint for Hubble to catch. Roth cautions that the original plume or smaller ones could still exist, just undetected by the telescope.
Europa may still be active in ways scientists can’t yet confirm from Earth. That uncertainty is part of why the next mission matters so much.
NASA’s Europa Clipper spacecraft is scheduled to arrive at Jupiter in April 2030, giving researchers a new chance to test the plume hypothesis directly. Roth says the mission could look for smaller phenomena than Hubble could detect, and he sounds genuinely energized by that prospect.
“I’m excited for Europa Clipper having the possibility and the instruments to find smaller things,” Roth says.
But he also underlines the patience the science may demand. “But I’m not too optimistic that we find evidence before Europa Clipper. We have another four years of not knowing.”
For now. the sharpest lesson from Hubble is also the most sobering: the evidence that Europa’s icy shell sometimes vents water into space—the signals that once seemed to point to cracks opening intermittently—has not held up across years of renewed scrutiny. The search continues. but the path may be narrower. and the stakes are clear: if plumes are weaker than hoped or rarer than claimed. getting samples from Europa’s environment will be harder—and life-hunting plans will have to adjust to what the moon is willing to show us.
Europa Hubble Space Telescope plumes hydrogen exosphere ultraviolet observations KTH Royal Institute of Technology Lorenz Roth Europa Clipper astrobiology Jupiter’s moons Astronomy & Astrophysics