Life has had plenty of opportunities to spread throughout the Milky Way galaxy over the eons, a recent study suggests — and our own Earth may be one of the key dispersal points.
The sun's random motion through space has brought it close to many other stars over the past 4.6 billion years. These close encounters likely jostle far-flung comets free from both systems, sending them careening toward the passing star, said study author Robert Zubrin, president of the Colorado-based company Pioneer Astronautics.
This "comet swapping" is probably responsible for many of Earth's past mass extinctions, Zubrin found. But the phenomenon has also likely aided life in the bigger picture, helping it hop from island to island across the vast ocean of space, he said.
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