Geysers on Jupiter's Moon Europa Have Disappeared
Almost exactly a year after NASA found evidence of water vapor on Europa, researchers from several different projects are claiming that the supposed geysers on Jupiter's icy moon are nowhere to be found, going so far as to assert that they may not exist at all.
Several studies have failed to replicate the original Hubble results that found plumes of water vapor on Europa. First, Hubble has been trained on Europa several times since the original discovery in order to confirm the results, but it hasn't been having any luck detecting the geysers. "We have not yet found any signals of water vapor in the new images so far," said team member Lorenz Roth.
SETI also analyzed NASA's Galileo data, which reflected observations of the Jupiter system from 1995 to 2003, and found no sign of the geysers. "I find it hard to believe that if a plume that was similar to the plumes we see on Enceladus had been going off on Europa during the Galileo era - I find it really unlikely that we would have missed it," said SETI researcher Cynthia Phillips. "I think we would have seen that thing."
NASA also didn't find any evidence of the geysers' existence when the Cassini spacecraft flew by the Jupiter system in 2001. "We found no evidence for water near Europa, even though we have readily detected it as it erupts in the plumes of Enceladus," said NASA's Larry Esposito in a statement.
If the geysers do not, in fact, exist, this discovery would have a significant impact on our search for extraterrestrial life. NASA recently predicted that Europa contains alien life under its icy surface, but this hypothesis hinges on the notion that Europa, like Enceladus, has a liquid ocean under that surface, and the geysers are the best evidence for the presence of liquid water.
However, NASA insists that these (admittedly disheartening) results do not necessarily indicate that the geysers do not exist at all, but rather that they are just not comparable to those on Enceladus. "It is certainly still possible that plume activity occurs, but that it is infrequent or the plumes are smaller than we see at Enceladus," said Amanda Hendrix, co-author of the NASA study. "If eruptive activity was occurring at the time of Cassini's flyby, it was at a level too low to be detectable by UVIS."
Similarly, Roth contended that geysers that go off more infrequently than those on Enceladus would be consistent with the original Hubble observations: "It was clear from the beginning that this is a transient phenomenon."