The first manned trip to Mars may seem a long way in the future but ESA has already started to solve the problem facing every traveller – just how do you fit everything you need in one suitcase? Not only will the first astronauts on Mars need to fit everything for a 3 year trip into one small spacecraft but they will not be able to throw anything away, including human waste. ESA has developed a new system called MELISSA (Micro-Ecological Life Support Alternative) to test ways of turning such waste into food, oxygen and water by creating an artificial ecosystem which uses micro-organisms to process the waste to use as fertilizer to grow plants. MELISSA is being developed with the help of several research organisation in Europe in a small pilot plant outside Barcelona, Spain.