A space probe called NEAR-Shoemaker made history last February when it became the first craft to land on an asteroid, a potato-shaped rock called 433 Eros. Not only did the 2,400-kilogram craft survive the descent onto Eros (SN: 2/17/01, p. 103), but measurements with its magnetometer a few days after landing confirmed a major mystery. Eros, indeed, has no detectable magnetic field.
That's puzzling because meteorites, which are believed to be fragments of asteroids, possess magnetic fields. How could a chip of an asteroid be magnetic if the parent asteroid isn't?
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