14 Years of Hubble Data Challenge Europa Water Plume Discovery: Scientists Question 2012 Observations
Summary: A team from New Mexico State University re-analyzing 14 years of Hubble Space Telescope observations of Jupiter's moon Europa has raised doubts about a 2012 claim to have detected water vapor plumes. The original claim of 99.9% confidence may have been statistical noise, though scientists cannot yet definitively rule out plume existence, which awaits resolution from NASA's Europa Clipper mission arriving in 2030.
Sources (original pages)
- space.com: Scientists thought Jupiter's moon Europa was ejecting water. Now they're not so sure（May 22, 2026）
Background
Europa, Jupiter's fourth-largest moon, has long been a focal point in the search for extraterrestrial life. Scientists believe a vast global saltwater ocean lurks beneath its icy shell, making it a prime candidate for harboring life elsewhere in the solar system. In 2012, astronomers using Hubble's STIS (Space Telescope Imaging Spectrograph) instrument detected Lyman-alpha emission signals near Europa, interpreting these as evidence of water vapor plumes erupting from fissures in the ice — signals that catapulted Europa to the top of astrobiology target lists.
Findings
The team, led by New Mexico State University astronomer William Retherford, revisited the 2012–2014 Hubble data as part of a broader 14-year dataset. However, the team acknowledged that detecting Europa's plumes had pushed Hubble to its absolute limits. Upon reanalysis, their confidence in the original 2012 plume detection has been shaken — the 99.9% confidence level initially reported may not be robust.
The team's research was published on May 5, 2026, in the journal Astronomy & Astrophysics.
Significance and Remaining Uncertainty
Despite the new doubts, scientists remain unable to conclusively rule out water vapor plume existence on Europa, especially given that similar plumes have been more confidently detected on other Galilean moons. The final answer may come in 2030 when NASA's Europa Clipper mission arrives in the Jovian system, capable of directly sampling any active plumes.
Europa, with its subsurface ocean, and an inset showing the Hubble Space Telescope. Credit: NASA