Life in Ice-Covered Oceans
Recent reports that Jupiter's satellites Europa and Callisto may have ice-covered oceans have fueled speculation that they may be inhabited by living organisms. Gaidos et al. analyze the thermodynamic requirements for life on Europa by analogy with life on Earth today and during past "snowball" Earth episodes. They conclude that nearly all metabolic life-styles on the present Earth will be denied to organisms on Europa and indicate which types of organisms, if any, are most likely to be found there.