Research funded by the European Space Agency into ways of feeding future astronauts on missions to Mars is about to find a very down-to-earth application — how to dispose of the sewage sludge left over after wastewater treatment. The MELISSA (Micro-Ecological Life Support Alternative) project, which ESA is funding in companies and research institutes throughout Europe, is developing a system of recycling as much of the waste as possible produced by astronauts on long-duration space missions into food and other consumables.