17 November 2011
New Europa fractured surface theory holds water - and maybe life
by Will Parker
Taking observations of Earth's ice sheets and floating ice shelves and applying them to Europa, scientists say Jupiter's moon may have a vast body of liquid water located relatively close to the surface under constantly fracturing ice sheets. The idea of liquid water under Europa's surface isn't new, but the authors of the new study have put forward the most compelling argument yet for how the bumpy features on Europa's surface were formed from upwelling water.
To arrive at the new hypothesis, the multi-institute team used Galileo spacecraft images of two roughly circular, bumpy features on Europa's surface called chaos terrains. Based on similar processes seen here on Earth - on ice shelves and under glaciers overlaying volcanoes - the researchers developed a four-step model to explain how the features form on Europa. It resolves several conflicting observations, some of which seemed to suggest that the ice shell is thick and others that it is thin.
The scientists have good reason to believe their model is correct, based on observations of Europa from the Galileo spacecraft and of Earth. Still, because the inferred lake is around 3 kilometers below the surface, the only true confirmation of its presence would come from a future spacecraft mission designed to probe the ice shell.
"This new understanding of processes on Europa would not have been possible without the foundation of the last 20 years of observations over Earth's ice sheets and floating ice shelves," said Don Blankenship, a co-author and senior research scientist at the Institute for Geophysics.
Lead author of the study, Britney Schmidt from The University of Texas at Austin, says the work strengthens the case for life existing on Europa. "The water could represent a potential habitat for life, and many more such lakes might exist throughout the shallow regions of Europa's shell," she said.
Further increasing the potential for life, the lake is covered by floating ice shelves that seem to be collapsing, providing a mechanism for transferring nutrients and energy between the surface and a vast ocean already inferred to exist below the thick ice shell.
"One opinion in the scientific community has been, 'If the ice shell is thick, that's bad for biology - that it might mean the surface isn't communicating with the underlying ocean,'" said Schmidt. "Now we see evidence that even though the ice shell is thick, it can mix vigorously. That could make Europa and its ocean more habitable."
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Source: University of Texas at Austin