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Comet Impact

It's Raining Comets

This artist's conception illustrates a storm of comets around a star near our own, called Eta Corvi. Evidence for this barrage comes from NASA's Spitzer Space Telescope, whose infrared detectors picked up indications that a giant comet or comets was recently torn to shreds after colliding with a rocky body in the inner system. In the illustration, one such comet is shown smashing into a rocky planet, splashing ice- and carbon-rich dust into space, while also smashing water and organics into the surface of the planet. The red line is an artistic lens flare, illustrating a flash from the collision. Yellow-white Eta Corvi is shown to the left, with still more comets streaming toward it.

Spitzer detected spectral signatures of water ice, organics and rock ­-- key ingredients of comets -- around Eta Corvi. This is the first time that evidence for such a comet storm has been seen around another star. Eta Corvi is just about the right age, about one billion years old, to be experiencing a bombardment of comets akin to what occurred in our own solar system at 600 to 800 million years of age, termed the Late Heavy Bombardment.

Scientists say the Late Heavy Bombardment was triggered in our solar system about 4 billion years ago by the migration of our outer planets, which jostled icy comets about, sending some of them flying inward. The incoming comets scarred our Moon and pummeled our inner planets. They may have even brought materials to Earth that were needed to kick start life.

Image Credit: NASA/JPL-Caltech/Johns Hopkins University Applied Physics Laboratory

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