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TITLE: Accretion: From Dust to Planets


Before there were planets, there were colliding grains of dust. The first gentle impacts clumped the dust particles together into bigger bits of matter, which themselves combined to make larger and larger bodies. Some bodies grew very large...only to be destroyed by enormous impacts. Others survived. Over time, these encounters created the present array of planets and asteroids. Today, the pockmarked surfaces of many of these bodies bear silent witness to this violent past.

[Photo: Asteroid Impact]





The Primordial Dust

Meteorites like Mezö-Madaras contain leftover samples of the actual dust and grains that formed the rocky planets 4.6 billion years ago. Called chondrites, meteorites of this type preserve direct evidence of the processes that shaped our Solar System.

The roughly spherical grains in Mezö-Madaras and in other chondrites are called chondrules. They are beautifully preserved, preplanetary grains that once drifted in the Solar System. Within the first few million years, the grains coalesced into the meteorite's parent asteroid.

This image is 31mm across.

  See caption at left.

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Smithsonian National Museum of Natural History Department of Mineral Sciences website Credits