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TITLE: How to Make a Planet


[Photo: Outer Space]

Rocky planets, moons, and asteroids all formed from the same material we now see in chondritic meteorites. Heat from impacts and radioactive decay warmed the interiors of these growing bodies. On small asteroids, the heat escaped quickly, and the bodies remained fairly homogeneous throughout. On larger asteroids and planets, however, the heat was not lost quickly enough, and the bodies began to melt. Their heavy metals coalesced and sank to form cores. Lighter, molten lava rose to the surfaces. Dense residues of solid minerals accumulated in the mantles.


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Dust and grains begin to clump together. Collisions between larger and larger objects produce an asteroid-sized body.

 

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The growing body heats up and begins to melt.

 

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Dense molten metal particles pool together and sink towards the center of the body. Lighter silicate liquid, or magma, rises towards the surface, leaving denser solid minerals in the mantle.

 

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The result: a layered, or differentiated, body with core, mantle, and crust.

 

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Meteorites are the main evidence we have for the evolution of the Solar System.


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