As this Galileo probe image shows, Europa's icy surface is cracked and jumbled — an indication of a sub-surface heat source. NASA
— Jumbled blocks of ice on the surface of Europa likely formed by melting action beneath.
— Studies show Jupiter's moon could have numerous large lakes beneath its icy shell, providing a habitat for life.
— Research also explains how nutrients and energy could get from the moon's surface to its buried ocean.
New research shows the jumbled ice blocks crowning the surface of Jupiter's icy moon Europa are signs of a large liquid lake the volume of the North American Great Lakes just below the surface, a key finding in the search for places where life might exist beyond Earth.
Drawing from studies of underground volcanoes in Iceland and Antarctica, scientists ran computer models to see if the chaotic formations on Europa's surface could be explained by the same geologic processes seen on Earth.
"We looked at melt underneath the ice and the fracture and collapse of ice shelves," Britney Schmidt, a postdoctoral fellow at the University of Texas at Austin's Institute for Geophysics, told Discovery News.
"We come with these large pockets of water that form lakes. As they melt they actually break up the ice above it, like what you see on Earth," she said.
"This is certainly the best model so far," Paul Schenk, a staff scientist with the Lunar and Planetary Institute in Houston, wrote in an email to Discovery News. "If we go back with penetrating radar instruments we should be able to see into the ice shell, determine the stratigraphy of the layers in the shell and verify which models works best."
Europa, which is slightly smaller than Earth's moon, is believed to have a large ocean of salty water deep beneath its frozen crust. These recently discovered lakes appear to be embedded closer to the surface.
"Europa has more water than all of Earth's oceans," planetary scientist Simon Kattenhorn, with the University of Idaho, told Discovery News.
While the ocean itself is of interest to scientists searching for life beyond Earth, a mechanism to churn the surface ice and subsurface water makes Europa an even more compelling target.
The vigorous mixing of ice and water provides one mechanism for nutrients and energy to get from the frozen surface to the ocean below.
"It's exciting for biology," Schmidt said.
A mission to Europa is second on planetary scientists' wish list after a sample return mission from Mars.
"Europa is likely to have a deep ocean of liquid water beneath its icy crust, making it an object of enormous interest as a possible abode for life," planetary scientist Steve Squyres, with Cornell University, testified at a Congressional hearing this week.
Schmidt's research will be published in a future issue of Nature and appears on the publication's website Wednesday.