Detail of metallic
surface of nickel-iron meteorite. The patterns in the texture, known
as "widmanstatten lines," are created as the molten nickel
and iron in the asteroid's core cool at the rate of one degree centigrade
per million years. The pattern of these lines forms a "fingerprint"
unique to each asteroid. Photo: Ron Hipschman.
Meteorite
samples courtesy of the
California Academy of Sciences
.