Icy Jupiter moon may be actively recycling its surface
Europa, the intriguing ice-encrusted moon of Jupiter, may be resurfaced through plate tectonics, scientists have discovered. The result would make Europa the only known body in the solar system besides Earth with plate tectonics, a process in which cold giant platters of crust—or in this case, ice—float around on top of warmer, more viscous layers in the body’s interior. The discovery also makes the moon more interesting in the search for extraterrestrial life, because the recycling action of plate tectonics would provide an important way to exchange chemicals between the surface and the water ocean that lies beneath the moon’s ice cap. Scientists have long known that Europa’s surface is geologically quite young, implying some form of resurfacing. And they have also previously identified expanding bands on the surface that appear to be providing fresh ice (pictured)—regions equivalent to the midocean ridges on Earth where new oceanic crust is formed. But they have been unable to explain where old ice on Europa is disposed of. Now, using images taken by the Galileo spacecraft, scientists have found evidence for missing ice—an area the size of Israel that must have gone somewhere. Reporting online today in Nature Geoscience, they invoke the term subsumption for explaining how the ice that was once in this missing area dove beneath other layers of ice—a process that would be analogous to subduction on Earth, in which oceanic crust falls beneath a continental plate.