Jovian icy moon Europa and volcanic moon Io transit the turbulent face of Jupiter, in this image captured by Voyager 1 on February 27, 1979 from 4,536,010 miles away (image mosaic credit: NASA/JPL/Björn Jónsson).

The gnarled, ruddy terrain of Thera Macula breaks up ice plains in the southern latitudes of the Jovian moon Europa, in this image from NASA’s Galileo probe. Thera, named for the Greek isle, came into intense focus this week as the theoretical site of a massive subsurface lake of salty liquid water, as proposed by a team of geophysicists and planetary scientists in the journal Nature (image credit: NASA/JPL/University of Arizona).