Habitable Space in the Solar System

This image shows a comparison of the potential habitable space available on Earth, Mars, Europa, Titan, and Enceladus. The green spheres represent the global volume with the right physical environment for most terrestrial microorganisms. On Earth, it includes parts of the atmosphere, oceans, and subsurface while deep below the surface of the other planetary bodies. Enceladus has the smallest volume but the highest habitat-planet size ratio followed by Europa. Surprisingly, it also has the highest mean habitability, in the Solar System, although too deep for direct exploration. Mars and Europa are the best compromise between habitability and accessibility. [links to the DPS09, press release, and original images].