Based on observations by NASA’s Galileo orbiter, they believe reservoirs of salty liquid may lie within the moon’s icy shell – some close to the surface of the ice and many miles below. A new study has suggested that shallow lakes cause plume or volcanic activity on the surface of the Jovian moon in its icy crust. The findings support the long-held idea that water could potentially erupt above Europa’s surface either as vapor plumes or as cryovolcanic activity. Further computer modeling in the research shows that if Europa has eruptions, they are more likely to come from shallow, wide lakes trapped in the ice rather than the deep ocean far below. Elodie Lesage, Europa scientist at NASA’s Jet Propulsion Laboratory in Southern California and principal investigator, said: “We showed that plumes or cryolava flows could mean there are shallow reservoirs of liquid below, which the Europa Clipper could detect. Our results give new insights into how deep the water driving surface activity, including plumes, can be. And the water should be shallow enough to be detected by multiple Europa Clipper instruments.” Lesage’s computer simulation offers a model of what scientists would discover if they looked inside the ice and saw explosions on the surface. Models predict they will find reservoirs in the upper crust 2.5 to 5 miles (4 to 8 kilometers), where the ice is coldest and most brittle, quite close to the surface. That’s because the underground ice there doesn’t allow for expansion: As pockets of water freeze and expand, they could crack the surrounding ice and cause explosions, like a soda can exploding in a freezer. And the pockets of water that would burst would probably be as wide and flat as pancakes. Deeper reservoirs, with floors more than 5 miles (8 kilometers) below the crust, would expand and push warmer ice around them. This ice is so soft that it acts as a cushion, absorbing pressure instead of bursting. These pockets of water would not behave like a soda can, but more like a liquid-filled balloon that stretches as the liquid inside freezes and expands. Don Blankenship of the University of Texas Geophysics Institute in Austin, Texas, who leads the radar instrument team, said: “The new work shows that bodies of water in the shallow subsurface could be unstable if the stresses exceed the strength of the ice and is associated with plumes that rise above the surface. That means REASON could see bodies of water in the same places you see plumes.” Europa Clipper will carry other instruments that can test the theories of the new research. The science cameras will be able to take high-resolution color and stereoscopic images of Europa. the thermal emission imager will use an infrared camera to map Europa’s temperatures and find clues about geological activity – including the cryovolcano system. If the plumes explode, they could be observed by the ultraviolet spectrograph, the instrument that analyzes ultraviolet light. Journal Reference:
