New research suggests the active geyser spotted on one of Saturn's moons may not contain liquid water after all, a finding that could hurt the chances of finding life there.
Last year the Cassini orbiting spacecraft photographed what appeared to be a geyser spurting out from the south pole of Enceladus, one of Saturn's moons.
Scientists were excited by the findings, with some speculating shallow pools of water lurking below the icy surface were causing the phenomenon.
But an alternative view to be published in Friday's issue of the journal Science said the chemical composition of the geysers makes it more likely they are made of ice clathrates.
Ice clathrates are lattice-like structures made of ice with gas molecules trapped inside.
Cassini found the geysers were a mix of water vapour, ice particles and significant amounts of carbon dioxide and methane. While methane cannot completely dissolve in liquid water, it can exist in a clathrate.
The study doesn't address whether liquid might be present anywhere else on the moon, said lead author Susan Kieffer, a planetary scientist at the University of Illinois at Urbana-Champaign. It only suggests no liquid water is required for the geyser to have occurred.
Cassini scientist Carolyn Porco said while the new model sounds plausible, it doesn't rule out her own model or the possibility of water flowing further down.
"There's reason to believe that there's enough warmth on Enceladus to support liquid water," Porco said.
Liquid water and a stable heat source are two conditions deemed necessary for supporting an environment favourable to life.
The 480-kilometre-diameter Enceladus, like Jupiter's Io and Neptune's Triton, is one of the few moons that have shown strong evidence of recent geological activity.