The Universe has a different face depending on which instrument pictures it. When seen by visible light in the Hubble Space Telescope it displays neither the youngest stars nor those reaching the final stages of their lives. All cold objects and those hidden within opaque clouds of dust will be missed. They are for the eyes of infrared space telescopes only. A new face of the Universe started to show up when the US-Dutch-British IRAS satellite inaugurated infrared space astronomy in 1983. It was, however, just a foretaste of what was to come.

Figure 53: ISO

The European Space Agency's Infrared Space Observatory (ISO) was launched in November 1995 and operated until April 1998. It delved much deeper into the dusty and cool Universe, looking for answers to the secrets of how galaxies, stars and planets formed, and where the crucial ingredients for life come from.

The water that we drink and which fills the world's oceans comes from the stars, and ISO saw water throughout the Universe, even in places where it was not thought to be present. These findings help in understanding how life appeared on Earth, and encourage expectations that living things exist elsewhere.

Figure 54: ESA/ISO LWS spectra M. Harwit et al., on HST (NASA & ESA) WFPC2 mosaic

ISO also detected large amounts of water vapour in the higher atmospheres of all the giant planets of the Solar System. This discovery was unexpected, and it implies that the planets have a continuous supply of cosmic water.

"The water comes simply from the interplanetary dust, which in turn is full of scattered grains from comets," said Helmut Feuchtgruber of the Max-Planck-Institut für Extraterrestriche Physik in Garching, Germany.

Figure 55: Water vapour in Titan's atmosphere. ESA/ISO SWS spectra Coustenis/Salama et al., on Voyager 2 (NASA) image	Especially exciting was the discovery of water in Saturn's largest moon, Titan, where ESA's interplanetary probe Huygens will examine environmental conditions that may be just too cold to bear life. Athena Coustenis of the Paris-Meudon Observatory and Alberto Salama of the ISO Data Centre at Villafranca, Spain, led the international team that found Titan's water.
		Athena Cousteris
"Water vapour makes Titan much richer", Athena Coustenis commented. "It will help us to understand the organic chemistry that took place also in the young Earth, since we are seeing a mixture of elaborate organic molecules closely resembling the chemical soup out of which life emerged."

	24. The long history of the chemical elements
	26. The cosmic cookery book for planets and life