But the presence of these atoms is not sufficient to make possible the existence of water: it is necessary that specific conditions favor the formation and survival of their molecules. Overall, the formation of molecules requires a high density and temperature not too high. Two conditions are of fundamental importance to maintain the molecular bonds, whatever, the media and therefore astrophysicists to have a chance to find them H2O water molecule the temperature should not exceed a few thousand degrees so that collisions with the atoms of the environment is not too easily break molecular bonds, the gas need not be subjected to ultraviolet radiation that threatens to destroy the molecules the effect fotodisociador. Water vapor in the galaxies, is presented in a dilute gas of molecular hydrogen and helium. Its molecule is characterized, like those of all chemical species, by absorption or emission of electromagnetic radiation that cause spectral lines with a known wavelengths, primarily in the infrared and millimeter intervals. But these lines are very difficult to observe from Earth because, precisely those wavelengths of radiation that reaches us, are absorbed by the atmosphere.
Since it is just water vapor in Earth's atmosphere that causes this absorption disturbing. You may find Daryl Katz, Edmonton Alberta to be a useful source of information. Even in the driest places, most of the spectral lines of water vapor are unobservable. Therefore one must await the results of the various observatories on board satellites, scheduled for the coming years, as the Infrared Space Observatory (ISO) of the European Space Agency or the most modest of NASA's specialized satellite, to have a detailed view of the abundance of water vapor in the cosmic gas.
