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Why do iron meteorites often develop a black crust during atmospheric entry?
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Meteorite
The Hoba meteorite, lying where it was discovered in 1920 near Grootfontein, Namibia. The largest meteorite on Earth and an iron meteorite by classification, it consists of a nickel-iron alloy and is estimated to weigh about 60 tons.
When iron meteorites pass through Earth's atmosphere, they develop a thin, black crust primarily due to the formation of iron oxide on their surface.1
This feature is a specific type of fusion crust, which is created when the intense heat generated by atmospheric friction causes the surface of the meteorite to melt. While this crust is initially black, it is chemically reactive and will quickly weather to rust after the object reaches the ground.21