Europa

NASA/JPL/University of Arizona

The icy surface of Europa is shown strewn with cracks, ridges and "chaotic terrain," where the surface has been disrupted and ice blocks have moved around. New laboratory experiments show that water ice and frozen sulfur dioxide react even at the frigid temperatures of Europa. Because the reaction occurs without the aid of radiation, it could take place throughout the moon's thick ice layer—an outcome that would revamp current thinking about the chemistry and geology of this moon and perhaps others.