Optical Microscopy of Meteoritic Metal

METAL SCIENCE Meteorite Thermal Histories | Expected Phase Transformations for Slow Cooling | Development of Chemical Zoning | Alternative Reaction Paths for Slow Cooling | Reaction Path for Fast Cooling The objective of meteorite metallography is to constrain the histories of meteorites and their parent asteroids. In the case of stony meteorites, metallographic studies complement the more traditional studies that are based on silicate mineralogy. The metallic components of meteorites provide unique insight into meteorite evolution because metals are responsive to thermal and shock processing at temperatures below silicate closure temperatures. In order to use metal microstructures as evolutionary indicators, it is essential to understand the phase transformation behavior of Fe-Ni alloys during cooling. The links above introduce the main phase transformations in Fe-Ni metal, and links these phase transformations to specific microstructures observed in meteorites. Gaspra, an S-type asteroid composed of silicates and metal.  Image is courtesy of NASA.