Origins and Distribution of Life in the Universe

Terrestrial life, defined as a chemical system capable of self-reproduction and also capable of evolution, probably originated from the evolution of reduced organic molecules in liquid water. We are looking for fossilised remnants in old sediments and also for a second genesis of life, artificial in a test tube or natural on another celestial body. On Earth, organic molecules might have been formed in the atmosphere, near hydrothermal vents or delivered by extraterrestrial dust grains. Life might have evolved on early Mars when water existed on the surface. Europa has probably a water subsurface ocean and perhaps hydrothermal systems harbouring a basic life form. The discovery of exoplanets opens the search for a second genesis of life to the whole Universe.