Meteors cross the atmosphere at speeds around 20 km per second. That is 72000 km/h or 44700 mi/h. This incredible velocity generates an enormous friction, causing the meteor to become so hot that emits light. This unique process creates extraordinary features that are exclusive to meteorites such as: fusion crust, flow lines, regmaglypts, orientation or rollover lips.
The outer layer of the descending rock melts due to the heat caused by friction. When it cools down, specially in stony meteorites there remain a very thin layer of dark color called fusion crust. Because rock transmits heat poorly, the inner part of the meteorite stays cold even when the exterior was melting.
Fusion crust in a 495g Aiquile
Sometimes fusion crust has a feature called flow lines. These lines result from the molten material being moved by the air like tiny lava rivers that solidify once the temperature goes down. It is typical in stony and iron meteorites.
Flow lines in a 451g Eucrite
Meteorites often acquire shallow soft pits on the surface that resemble a thumbprint. These marks are called regmaglypts and are due to ablation. They typically appear in iron meteorites although stony meteorites can display them too.
Regmaglypts in a 4082g Sikhote Alin
If the meteor maintains a fixed orientation enough time without tumbling erratically, it develops a rounded conical shape called orientation. Many times orientation is accompanied by radial flow lines and rollover lips. Oriented meteorites represent a small percentage but they are not considered rare.
Orientation & rollover lips in a 50g Chelyabinsk
Sometimes the molten incandescent layer moves towards the back of the falling meteor with enough material to create rims. They are called rollover lips and are found on the back of oriented pieces or in big regmaglypts, where this material accumulates since it is temporarily protected from friction by aerodynamics.