Do Europa’s Water Plumes Really Exist? New Study Reopens Debate
New research by planetary scientists at the Southwest Research Institute and the KTH Royal Institute of Technology suggests that evidence of vapor rising from Jupiter’s icy moon Europa may be less conclusive than once thought.
This is an artist’s impression of a water vapor geyser on Europa. Image credit: University of Cologne.
“The evidence for water vapor plumes over Europa is not as strong as we initially understood,” said Dr. Kurt Retherford, a researcher at the Southwest Research Institute, one of the authors of a 2014 paper initially making the claim.
In the new study, Dr. Retherford and his colleague analyzed data collected by the Space Telescope Imaging Spectrograph (HST/STIS) aboard the NASA/ESA Hubble Space Telescope in 1999 and between 2012 and 2020.
They focused on Europa’s Lyman-alpha emission, a specific wavelength of ultraviolet light emitted and scattered by hydrogen atoms.
“One of the difficulties in interpreting the data at the time was determining where to place Europe in context,” Dr Retherford said.
“The way Hubble works leaves some uncertainty in terms of placement relative to the center of the image.”
“If Europa’s placement was off by even a pixel or two, it could affect how the data is interpreted.”
As a result, what the researchers thought was evidence of a water vapor plume might also simply be statistical noise.
“Our reanalysis took our initial 99.9% confidence in the existence of the plumes and reduced it to less than 90% confidence,” said Dr Lorenz Roth, a researcher at the KTH Royal Institute of Technology.
“It’s simply not enough evidence to support the certainty of the claims we made at the time.”
“The current dataset does not rule out the possibility of the water vapor plumes described in the 2014 paper, but it no longer provides concrete evidence for them,” Dr Retherford said.
“The description of phenomena no longer holds the same ground. »
“The new data has led us to reconsider the strength of the previous paper’s conclusion regarding water vapor plumes.”
“The recent analysis also provides improved information on the neutral hydrogen atom component of Europa’s fleeing atmosphere, originating from its water ice surface.”
“We still hope to find plumes of water vapor escaping from Europa.”
“Similar water vapor plumes have been confirmed on Saturn’s moon Enceladus, and Europa’s neighbor Io, another moon of Jupiter, has plumes of sulfur dioxide extending into space.”
The team’s new article was published May 5 in the journal Astronomy and astrophysics.
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L.Roth and others. 2026. Lyman-α emissions from Europe from HST/STIS observations. A&A 709, A59; doi: 10.1051/0004-6361/202659406
