Reddish spots on the icy surface of Jupiter's moon Europa may indicate pockets of warmer ice rising from below. This upwelling could provide an elevator ride to the surface for material in an ocean beneath the ice, say scientists studying data from NASA's Galileo spacecraft.

Image credit: NASA/JPL/University of Arizona/University of Colorado

The spots and shallow pits pepper the enigmatic ridged surface of Europa in this picture combining information from images taken by Galileo during two different orbits around Jupiter.

The spots and pits visible in this region of Europa's northern hemisphere are each about 10 kilometers (6 miles) across. The dark spots are called "lenticulae," the Latin term for freckles. Their similar sizes and spacing suggest that Europa's icy shell may be churning away like a lava lamp, with warmer ice moving upward from the bottom of the ice shell while colder ice near the surface sinks downward. Other evidence has shown that Europa likely has a deep melted ocean under its icy shell. Ruddy ice erupting onto the surface to form the lenticulae may hold clues to the composition of the ocean and to whether it could support life.

The image combines higher-resolution information obtained when Galileo flew near Europa on May 31, 1998, during the spacecraft's 15th orbit of Jupiter, with lower-resolution color information obtained on June 28, 1996, during Galileo's first orbit.

"Europa acts like a planetary lava lamp, carrying material from near the surface down to the ocean, and, if they exist, potentially transporting organisms up toward the surface," said Dr. Robert Pappalardo, a planetary scientist at the University of Colorado, Boulder.

The Galileo spacecraft, orbiting Jupiter since 1995, has produced strong evidence that Europa has a deep ocean of melted saltwater underneath a surface layer of ice.

The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Galileo mission for NASA's Office of Space Science, Washington, D.C.