Is there water in the Cosmos? This fascinating question is under discussion since long ago in the scientific community. We now know that the water molecule is concentrated, in the form of ice and vapor, some privileged places, mainly in certain clouds cold of our galaxy. But only the solar system contains significant concentrations of water and only the ground has its form liquid. Why land enjoys the privilege? Where water comes from and how it has formed? In this article is recontruye its history, since its formation in the environment of the cold stars up to their last adventure in the planets of the solar system. It is found in form of vapour or ice in the atmosphere of some stars in molecular clouds, in numerous satellites of ice in the solar system, comets and planets of the solar system. But what is exceptional is the presence of water in liquid state: the Earth is the only currently known place in which water occurs in this way. Where does so indispensable to life Earth water come from? That survives, and so sparsely in liquid form? To understand what astronomers have reconstructed the adventure of water in the Cosmos that begins around certain cool stars and that leads, after the formation of the solar system, to the water and ice present in the planets. Water can form naturally in various regions of the universe from their constituents – H hydrogen and oxygen 0-.
Hydrogen represents more than 70% of the mass of the universe visible. With regard to oxygen, it is about 1%. But the presence of these atoms is not enough to make possible the existence of water: it is necessary that specific conditions conducive to the formation and survival of its molecules. In general terms, the formation of molecules requires high density and not too high a temperature.