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Planetary Bombardment

December 29, 2011

As the Moon descends the western sky this evening, look about halfway along its crescent for a couple of dark round dots. Those are impact basins that formed when giant comets or asteroids slammed into the lunar surface. Molten rock bubbled up to fill the impact basins, creating volcanic plains.

These and similar features probably formed about four billion years ago, when the inner solar system was bombarded by comets and asteroids. The fusillade hit Earth, too — perhaps bringing the water and organic compounds necessary for life.

If any planets orbit close to a star in the constellation Corvus, they may be undergoing a similar bombardment right now.

Observations by Spitzer Space Telescope show a giant disk of ice and dust around Eta Corvi, which is a bit bigger and brighter than the Sun. It’s about the same age the Sun was when the bombardment of the inner solar system took place.

The disk’s composition and location suggest it formed when a giant comet slammed into a rocky planet close to the star, splashing debris far and wide.

A much larger disk also encircles the star — a possible storehouse of comets. Movements of possible planets could be disrupting the orbits of the comets — sending some of them to blast the inner regions of the system.

Corvus is well up in the south at first light, and forms a shape that resembles a sail. Eta Corvi is a faint star near the top left corner — a star whose planets may be taking a beating.


Script by Damond Benningfield, Copyright 2011


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