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Building planets

Part of Hall of Meteorites.

Building Planets section at the Hall of Meteorites. C. Chesek/©AMNH

 

Pieces of asteroids and planets that fall to Earth as meteorites reveal the processes at work deep inside planets-including our own.

The farmland near Brenham, Kansas, is flat and almost entirely free of rocks-yet farmers in the 1880s occasionally bent their plows on mysterious metallic objects. Homesteader Eliza Kimberly noticed that the odd black rocks resembled a meteorite she had seen as a schoolgirl in Iowa. Despite teasing from her husband and neighbors, she collected a large pile of the "iron rocks," and after five years of letter-writing she convinced a scientist to look at them. They were indeed meteorites.

The remarkable Brenham meteorite fragments contain gemlike olivine crystals embedded in an iron-nickel alloy. Billions of years ago, this rock and iron mixture formed when a large asteroid melted and separated into an iron co