Recent scientific endeavors spearheaded by planetary researchers affiliated with the Southwest Research Institute and the KTH Royal Institute of Technology indicate that the purported evidence of vapor expelling from Jupiter’s frigid moon Europa might be less definitive than previously posited.
This is an artist’s impression of a water-vapor geyser on Europa. Image credit: University of Cologne.
“The substantiation for water vapor effusions on Europa is not as robust as our initial comprehension suggested,” commented Dr. Kurt Retherford, a scientist at the Southwest Research Institute and a contributor to a 2014 publication that originally posited such a claim.
In the scope of the latest investigation, Dr. Retherford, in collaboration with his colleague, meticulously examined data procured by the Space Telescope Imaging Spectrograph (HST/STIS) integrated within NASA/ESA’s Hubble Space Telescope, specifically data from 1999 and the intervals spanning 2012 through 2020.
Their analytical focus was directed towards Europa’s Lyman-alpha emission, a distinct spectral signature of ultraviolet radiation produced and disseminated by hydrogen atoms.
“A primary challenge in interpreting the historical data involved accurately situating Europa within its observational frame,” Dr. Retherford elaborated.
“The operational methodology of the Hubble telescope introduced a degree of imprecision concerning its precise positioning relative to the image’s central point.”
“A minor deviation, even of a single pixel or two, in Europa’s placement could significantly influence the interpretation of the acquired data.”
Consequently, what the research team initially perceived as indicators of a water vapor plume might, in fact, be attributable to statistical anomalies or noise within the dataset.
“Our re-evaluation has downgraded the initial 99.9% certainty regarding the existence of these plumes to a confidence level below 90%,” stated Dr. Lorenz Roth, a researcher from the KTH Royal Institute of Technology.
“This level of statistical assurance is insufficient to substantiate the definitive pronouncements made at that juncture.”
“While the contemporary data set does not entirely dismiss the potential occurrence of the water vapor plumes detailed in the 2014 publication, it no longer furnishes compelling, direct evidence for them,” Dr. Retherford clarified.
“The description of the phenomenon no longer possesses the same degree of corroboration.”
“The newly acquired data necessitate a reassessment of the strength underpinning the conclusions presented in the antecedent paper concerning water vapor emissions.”
“Furthermore, the recent analysis offers enhanced insights into the neutral hydrogen atom constituent of Europa’s tenuous atmosphere, which originates from its surface composed of water ice.”
“Our aspiration to definitively identify water vapor plumes emanating from Europa persists.”
“Comparable water vapor eruptions have been unequivocally verified on Enceladus, Saturn’s moon, and Io, Jupiter’s adjacent moon, also exhibits plumes of sulfur dioxide that dissipate into space.”
The research team’s latest scholarly article received publication on May 5th within the esteemed journal Astronomy & Astrophysics.
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L. Roth et al. 2026. Europa’s Lyman-α emissions from HST/STIS observations. A&A 709, A59; doi: 10.1051/0004-6361/202659406
