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Building planets

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Exhibition Text

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 core and a rocky crust. Meteorites that come from the deep interiors of such asteroids provide tantalizing clues about the interior of Earth and other planets.

For Educators

Topic: Astronomy

Subtopic: Planets

Keywords: Astrophysics, Olivine, Iron-nickel alloys, Astrogeology, Asteroids, Planets--Geology, Meteorites, Iron

Audience: General