1, surface melting shell. Meteorites must pass through the dense atmosphere before falling to the ground. In the process of falling, the meteorite rubs against the atmosphere to produce high temperature, which melts its surface and forms a thin molten shell. Therefore, all newly landed meteorites have a black molten shell with a thickness of about1mm.
2. Surface air imprint. In addition, due to the interaction between meteorites and airflow, there will be many air traces on the surface of meteorites, just like fingerprints pressed by fingers. Gas imprint is one of the characteristics of meteorites, and gas imprint of meteorites is the trace left by ablation between meteorites and high temperature airflow when landing.
3. Internal metal. Iron meteorites and stony iron meteorites are composed of metallic iron with high nickel content (5% ~ 10%). There are also metal particles in chondrites, and fine metal particles can be seen on fresh fractures.
4. magnetism. Because most meteorites contain iron, 95% meteorites can be attracted by magnets.
Formation of meteorites
When meteorites fly at high altitude, the surface temperature reaches several thousand degrees. At such a high temperature, the surface of the meteorite melts into liquid. Later, due to the blocking of the dense atmosphere in the lower layer, its speed became slower and slower, and the molten surface cooled down to form a thin shell called "molten shell". The molten shell is very thin, generally about 1 mm, and the color is black or brown.
During the cooling process of the molten shell, the traces of air flow on the surface of the meteorite are also preserved, which is called "air mark". The air mark looks like a finger mark pressed on the dough. Molten crust and gas marks are the main features of meteorite surface. If you see a molten shell or air mark on the surface of a stone or iron block, you can immediately conclude that it is a meteorite.