Astrophysicists have detected the first signs of cold water vapor in the outer reaches of a baby star system. The discovery, announced today in Science, not only fills a gap in the convoluted question of how planets form, but also hints where the water that covers Earth-like planets is stored until the rocky bodies can receive and hold onto it as oceans.
The short version of how scientists believe the Earth formed goes like this: Roughly 4.5 billion years ago, the solar system was a spinning disk of gas and dust that looked something like a record, and one groove in that record collapsed into a molten orb that became our planet. About 700 million years later, when Earth was crusty and dried-out, comets, asteroids and other watery space wanderers bombarded the world. In just tens or hundreds of thousands of years, these impacts deposited our life-giving water.
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