Origins and Importance of Water

The origin of water on Earth, and its formation in deepest space.

Water is so uniquely favorable to life as we know it, it is hard to imagine life without it. Where did it come from, this planetary wrap of fluid, this liquidy bower? A standard story is that the heat of the young Earth drove hydrogen and oxygen out of chemical combination in minerals like mica, and these atoms then combined to form water. Four billion years ago the planet was mostly molten, heated by radioactivity and the violence of its formation—a vast spherical volcano—and the newly formed water bubbled up out of the fiery depths as steam. Later, as the planet cooled, the Earth's shroud of gaseous moisture precipitated as rain, which collected in the broad, deep hollows of the newly formed crust to form the first oceans. "Our oceans were once our rocks," the chemist P W Atkins says of this scenario. Another possibility is that the water was already there in the gassy nebula out of which the solar system formed. A team of astronomers using the Infrared Space Observatory have observed what appears to be a massive water generator in a gas cloud in the constellation Orion, 1,500 light-years away The Earth-orbiting telescope picked up the unmistakable spectral signature of water molecules, the largest concentration of water ever seen outside of our solar system. Like most interstellar gas clouds, the target nebula in Orion is mostly hydrogen, but it also contains free oxygen. A hot young star embedded in the cloud spews off powerful shock waves that pummel and heat the gas, causing oxygen to combine with hydrogen, creating enough water every single day to fill the Earth's oceans sixty times over. Eventually, the water vapor in the nebula will cool and freeze into small particles of ice, and particles such as these may have been present within the dusty cloud out of which our solar system formed, 5 billion years ago.