One of the major revolutions in planetary science that I’ve seen in my lifetime is the discovery that the solar system contains not just one ocean world – our Earth – but several ocean worlds. Unlike or planet, which has its oceans on the surface, these other worlds trap their oceans beneath a surface layer of ice (or in the possible case of the asteroid Ceres, beneath a rocky shell). For several of these worlds such as Jupiter’s moons Ganymede and Callisto, the oceans appear to be locked between layers of ice and therefore would be unlikely candidates for abodes of life. For two of the moons, Jupiter’s Europa and Saturn’s Enceladus, the oceans appear to lie directly on top of a rocky core that would provide key elements needed to support life as well as energy from possible hydrothermal vents. Saturn’s moon Titan is a unique case, with seas of liquid ethane, methane, and propane on the surface and a water ocean in the interior that may or may not be in contact with the rocky core and occasionally interact with the surface. (This article and poster give more background on these worlds and their oceans.)
NASA’s managers, at the direction of Congress, have begun to put together an Ocean Worlds program to explore Europa, Titan, and Enceladus. At a recent meeting of an advisory group for NASA, the Committee on Astrobiology and Planetary Science (CAPS), Jim Green, the head of NASA’s Planetary Science Division, and Barry Goldstein, from the Jet Propulsion Laboratory, provided updates on plans to explore these worlds. In this post, I’ll report on the highlights of their talks (the presentations will be posted to this site (scroll down to the March 29-31 meeting) sometime in the future).