MELiSSA or 'Micro Ecological Life Support System Alternative' refers to a research program managed by the European Space Agency. It aims to develop an artificial ecosystem for (bio)regenerative life support during long-term space missions e.g. to Mars. The project is a collaborative effort of 14 core partners (including VITO) and numerous supporting organizations.  The MELiSSA initiative is internationally recognized as the most advanced effort to develop artificial life support systems. VITO activities focus on membrane bioreactor systems and on the fate and effect of microcompounds during closed loop operation.