Flight features of meteorites

Meteoroids cross the atmosphere at speeds around 20 km per second. That is 72000 km/h or 44700 mi/h. This incredible velocity generates very specific conditions that affect the shape of the meteor and creates in it some extraordinary features that are (almost) exclusive to meteorites such as: fusion crust, flow lines, regmaglypts, orientation or rollover lips. The reason why they are not exclusive to meteorites is the human-made objects returned from space that can develop similar features (fusion crust and flow lines) despite its proportionally slower but still incredible velocity. But let’s continue with our flight features of meteorites:

 

Fusion crust

Fusion crust is a dark and glassy layer formed as the meteoroid’s surface melts during atmospheric entry. The intense heat, that ranges from 870 to 1650 °C (1600 to 3000 °F), is generated by air compression and ionization at hypersonic speeds. This heat causes the outer material to melt and ablate, exposing fresh material beneath to the same process. Ablation continues as the meteoroid descends, rapidly stripping away mass. Meteoroids typically lose most of their mass through this process.


Once the meteoroid slows enough for melting to stop, the final layer of molten material solidifies into a crust, typically 1-2 mm thick on stony meteorites. Despite the extreme heat outside, the interior remains cold due to the rock’s poor thermal conductivity.


The crust retains the meteorite’s overall composition but is altered by melting and oxidation. Over time, this distinct feature may fade due to terrestrial weathering, particularly in humid environments, but it remains a key feature for identifying meteorites.

5 Flight Features that will help you indentify a meteorite.

Fusion crust in a 495g Aiquile

Flow lines

Flow lines are patterns that form on the surface of a meteorite’s fusion crust, created by the movement of molten material as it melts and flows across the meteorite during its descent through the atmosphere. The molten material, shaped by aerodynamic forces and gravity, flows backward over the surface and solidifies as the meteoroid cools.

 

The resulting flow lines often align with the direction of the meteorite’s travel, providing clues about its orientation and trajectory during atmospheric entry. They are typical in stony and iron meteorites.

5 Flight Features that will help you indentify a meteorite.

Flow lines in a 451g Eucrite

Regmaglypts

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. Other pictures of regmaglypts here.

5 Flight Features that will help you indentify a meteorite.

Regmaglypts in a 4082g Sikhote Alin

Orientation

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 and are usually very appreciated by collectors for their untuitively recognizable shape’s origin. It is easy to imagine how that is a meteorite and why it has that shape.

5 Flight Features that will help you indentify a meteorite.

Orientation & rollover lips in a 50g Chelyabinsk

Rollover lips

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.

 

 

 

Identify a meteorite

Although these 5 flight features are mostly unique of meteorites (and also some space junk falling back on Earth), they might not be very obvious in some meteorites, specially if the meteorite has a long terrestrial age, that means that the meteorite has been on Earth for a long time. So there are more things you can learn on How to Identify a Meteorite.

 

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