What distant planet is covered with ice and vast liquid oceans, is active enough for the ice to be constantly renewed (thus erasing impact craters and creating a mostly smooth surface), yet has gigantic cracks and ridges that imply convection currents? Convection means heat, and heat + liquid water = prime candidate for life.
Well, it’s not a planet, and it’s not very far away (relatively speaking, of course). It’s Europa, one of Jupiter’s largest moons, and NASA recently released this splendid image to pique our imaginations. This is a mosaic made from photos collected by the Galileo probe in the late 90s, reprocessed to create a high-resolution image that shows the moon as we’d see it through our own eyes.
A little detail from NASA’s explanation:
Color variations across the surface are associated with differences in geologic feature type and location. For example, areas that appear blue or white contain relatively pure water ice, while reddish and brownish areas include non-ice components in higher concentrations. The polar regions, visible at the left and right of this view, are noticeably bluer than the more equatorial latitudes, which look more white. This color variation is thought to be due to differences in ice grain size in the two locations.
I can never look at Europa without thinking of Arthur C. Clarke and 2010: Odyssey Two (“ALL THESE WORLDS ARE YOURS EXCEPT EUROPA. ATTEMPT NO LANDING THERE”). Despite the continued defunding of NASA and the downscaling of so many great projects, I still live in hope that in my lifetime, we really will attempt a landing there.
(Click the image to embiggen.)