Image: New research suggests that some of the small rocky bodies that smashed together to form planets, called planetesimals, had magnetic fields. Damir Gamulin, courtesy of Benjamin WeissFrom Earth Magazine:
Even before the birth of the planets, our solar system was hardly a lonely place. Small rocky bodies, called planetesimals, filled the inner solar system, eventually colliding together to form the planets. Now a new look at a group of ancient meteorites shows that at least some planetesimals generated their own magnetic fields — a feat many scientists thought extremely difficult for such small astronomical bodies. The work also has scientists rethinking how planets formed.
Most meteorites don’t make it to Earth unscathed. After repeatedly smashing into other objects and traveling through Earth’s harsh atmosphere, they can be substantially altered before crash-landing on the planet. But not angrites — a group of 12 stony meteorites that, at an age of about 4.56 billion years old, are among the oldest-known rocks in the solar system and somehow “got here without being messed up,” says Benjamin Weiss, a planetary geologist at MIT in Cambridge, Mass. Because these meteorites are pristine, angrites retain information about the larger body from which they came.
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