Europa’s “Great Lake.” Scientists speculate many more exist throughout the shallow regions of the moon’s icy shell. Image: Britney Schmidt/Dead Pixel FX/University of Texas at Austin.
In a significant finding in the search for life beyond
Earth, scientists from The University of Texas at Austin and elsewhere have discovered what
appears to be a body of liquid water the volume of the North American Great
Lakes locked inside the icy shell of Jupiter’s moon 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, lead author Britney
Schmidt, a postdoctoral fellow at The University of Texas at Austin’s Institute for Geophysics,
writes in Nature.
Further increasing the potential for life, the newly
discovered 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,'” says 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.”
The scientists focused on 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
“I read the paper and immediately thought, yes, that’s
it, that makes sense,” says Robert Pappalardo, senior research scientist
at NASA’s Planetary Science Section who did not participate in the study.
“It’s the only convincing model that fits the full range of observations.
To me, that says yes, that’s the right answer.”
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 lakes are several kilometers below the
surface, the only true confirmation of their presence would come from a future
spacecraft mission designed to probe the ice shell. Such a mission was rated as
the second-highest priority flagship mission by the National Research Council’s
recent Planetary Science Decadal Survey and is currently being studied by NASA.
On Earth, radar instruments are used to image similar features within the ice,
and are among the instruments being considered for a future Europa mission.
“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,” says Don Blankenship, a co-author
and senior research scientist at the Institute for Geophysics, where he leads
airborne radar studies of Earth’s ice sheets.