fusion crust
A charred layer on a meteorite formed
by the freezing of surface melt at the end of a meteorites high-speed atmospheric
flight. When a meteorite tears through the atmosphere at between 12 and
72 km/s, friction with the air can raise its surface temperature to 4,800
K. At these temperatures the surface minerals melt and flow backwards over
the surface. As the meteorite slows and the fireball is extinguished, the
molten minerals begin to cool and fuse together to form a thin, glassy skin
which envelopes the whole meteorite. Often the fusion crust is black or
bluish-black though it can be light colored and transparent. It helps to
make the meteorite stand out against the background of terrestrial rocks.
Related category
• METEORS
AND METEORITES
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