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Building Planets

Building planets

  • 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.

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  • For Educators

    • Topic: Astronomy

      Subtopic: Planets

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

      Audience: General

In This Section

C.1.1.1. Brenham

Brenham (AMNH 3813)

The Brenham meteorite scattered more than three tons of meteorite fragments in the vicinity of Brenham, Kansas. 

C.2. CRUST_min


As the solar system formed more than four billion years ago, primitive particles collided and clumped into larger and larger bodies.

C.3. MANTLE.jpg


Why have no meteorites been found from an asteroid's olivine mantle? Here are a few theories.



Without Earth's molten outer core, life as we know it would not exist. 

C.5. IRON CRYSTALS min.jpg

Iron crystals

In the metal cores of partially molten asteroids, iron-nickel alloys crystallized in a distinctive pattern known as the Widmanstätten structure. 

C.6. VESTA min.jpg


Between the orbits of Mars and Jupiter, there is a wide gap. 

C.7. MARS min


Pieces of Mars that fall to Earth as meteorites gave us our first samples of the surface of another planet.

C.9. LOCAL IMPACT min.jpg

Peekskill meteorite

Falling just a short distance from New York City, this meteorite became famous for its unusual landing.

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