Life and Death
The comets and asteroids that orbit the Sun can be dangerous. They can slam into Earth, devastating life across large areas. An asteroid that exploded above Siberia a hundred years ago, for example, flattened hundreds of square miles of forest. And impacts by bigger objects may have killed life around the entire planet.
Yet in a cosmic irony, comets might have brought the ingredients for life to Earth in the first place.
Comets are big balls of frozen water and gases mixed with rock. They're left over from the birth of the solar system four and a half billion years ago.
In fact, comets and asteroids were the building blocks for Earth and the other planets. Plenty of them were still around after Earth was born, so they continued to bombard our planet. A comet can contain millions of tons of water, so it's possible that comets brought much of the water that fills Earth's oceans.
Comets contain many other compounds besides water. Some of them form the basic ingredients for life. So comets could have deposited the materials that gave birth to life on our planet.
And a recent study suggested that life was actually born inside comets instead of on Earth itself. Other scientists disagree, and don't think that comets are good incubators for life. Even so, it's possible that the bodies that have likely killed off a lot of the life on Earth over the eons also provided the raw materials for life to form in the first place.
Script by Damond Benningfield, Copyright 2008
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