Water Vapor Found Venting off Europa

Water vapor detected near the south pole of Jupiter's moon Europa represents the strongest evidence yet of water plumes erupting off the surface of the space body long believed to possess an ocean beneath its icy surface.

Though more research is needed in order to confirm the source of the water vapor, researchers say they are fairly confident they've got it right.

"By far the simplest explanation for this water vapor is that it erupted from plumes on the surface of Europa," said lead author Lorenz Roth of Southwest Research Institute in San Antonio.

And if that's the case, those plumes could provide a window into the ocean below the moon's icy crust, allowing future studies to "directly investigate the chemical makeup of Europa's potentially habitable environment without drilling through layers of ice," Roth said. "And that is tremendously exciting."

Saturn's Enceladus is the only other moon known to contain water plumes, which were discovered by NASA's Cassini orbiter in 2005. The new study, published in Science Express, has only detected water vapor on Europa, whereas Encedalus' plumes contain dust and ice particles, too.

In order to gather the data, the researchers had to push the Hubble Space Telescope "to its limits," according to Joachim Saur of the University of Cologne and principal investigator of the Hubble observation campaign.

Roth said the long cracks on Europa's surface, called lineae, could be acting like vents through which the water vapor escapes into space, similar to the fissures that host Enceladus' jets.

Like those found on Enceladus, Europa's plumes vary depending on the moon's position in its orbit, with no signs of venting when it draws close to Jupiter. One possibility for this is that the lineae are pulled apart when the moon is farther away due to more stress brought on by gravitational tidal forces pushing and pulling on the lunar body.

"The apparent plume variability supports a key prediction that Europa should tidally flex by a significant amount if it has a subsurface ocean," said Kurt Retherford, also of Southwest Research Institute.

Either way, the discovery could have significant implications in the ongoing search for life beyond our planet.

"If confirmed, this new observation once again shows the power of the Hubble Space Telescope to explore and opens a new chapter in our search for potentially habitable environments in our solar system," said John Grunsfeld, an astronaut who participated Hubble servicing missions and now serves as NASA's associate administrator for science in Washington.