The case for water plumes on Europa just got much harder to make
Europa’s faint glow in ultraviolet light once looked like a possible water plume punching through ice. After 14 years of Hubble data, that signal now looks far less certain. Meanwhile, a different picture of the moon’s escaping hydrogen atmosphere comes into sharper view. Europa has long tempted scientists with the same question. If a salty ocean lies beneath its ice, can any of that buried water break through to space? For a time, one set of Hubble observations seemed to hint that the answer might be yes. A bright patch seen in ultraviolet light near the moon’s limb was interpreted in 2014 as possible evidence of a faint water vapor plume. Now, after a much broader reanalysis of Europa observations from 1999 and 2012 through 2020, that case has weakened sharply. “The evidence for water vapor plumes on Europa isn’t as strong as we first understood it,” Southwest Research Institute scientist Kurt Retherford said. Retherford was part of the team behind the earlier plume claim and is also an author of the new reanalysis. The …
