Simulated space ice. Light micrograph of vesicles (round structures) in ice formed under conditions simulating those in space. Mixtures of the common space molecules, such as water, ammonia and simple hydrocarbons, were frozen at low temperatures and then exposed to ultraviolet radiation to simulate sunlight. The vesicles, 10 micrometres wide, show membrane-like properties, a possible precursor to cellular life. Products from the experiments also included complex biological molecules. The results support the theories that the origin of Earth, and other life, involved space ices impacting planets and depositing organic materials. Photographed at NASA's Ames Research Center, California, USA.