The new discipline of astrobiology – that is, the science of searching for extraterrestrial life – is not only rapdly growing, but has also captured the public imagination. This unit examines the emergence of icy satellites of distant planets as potential sites of extraterrestrial life. Focussing on the case study of Jupiter's moon Europa, the unit looks at the potential for life there, and speculates on the ethics of searching for life elsewhere in the solar system. This study unit is just one of many that can be found on LearningSpace, part of OpenLearn, a collection of open educational resources from The Open University. Published in ePub 2.0.1 format, some feature such as audio, video and linked PDF are not supported by all ePub readers.