Russian mathematicians and physicists calculated consequences of possible collisions of natural cosmic bodied with our planet’s atmosphere and surface, and worked out a collision classification.

Our planet’s atmosphere hampers a flying body, and incoming air flow takes away part of its mass. As the body keeps flying, air becomes denser, and its resistance grows, thus either stopping the body somewhere above the ground, or not preventing it from reaching Earth’s surface. Large bodies tend to split into smaller ones during flying in Earth’s atmosphere. Researchers solved equations of meteor physics, describing dependence of body’s speed and weight from flight altitude, which helped them create a classification of collision consequences. Equations’ solution depends on two dimensionless characteristics, which define slowdown altitude and contribution of ablation process during moving of a cosmic body in atmosphere.

Researchers came out with four possible scenarios, taking place after a cosmic body enters Earth’s atmosphere. If a space invader is very heavy, atmosphere has extremely small effect on it. A meteorite reaches the Earth’s surface and hits it, leaving a crater. Barringer meteorite crater, located in Arizona, United States, which is 175 meters deep and has 1265 meters in diameter, is a good example for such a scenario. This crater appeared a very long time ago.

 

 

When both mentioned characteristics don’t exceed 1, a cosmic body gets destroyed in Earth’s atmosphere with only fragments of it reaching the planet’s surface. In this case, we can see crater and meteorite fields. For example, February 12, 1974 is notable for the famous Sikhote Alin meteorite shower, which took place n Russia Far East and left numerous meteorite craters and holes. Modern mathematical models for drifting of clouds, made of fragments, allow predicting main geometrical and other characteristics of such fields. When parameter values tend to 1, a meteorite mainly evaporates in the atmosphere and splits into tiny fragments, weighing no more than 10 kilograms altogether. These small meteorites do not leave any craters.

Another scenario takes place when a meteoric body is not stopped by Earth’s atmosphere, but loses mass by evaporating. Earth’s surface is attacked by a high-speed stream of air and vapour. This gas spreads along the surface and forms areas of high pressure. A good example is famous Tunguska meteorite, which hit the Earth on June 30, 1908.

Researchers say that their classification can be extended. They suggest analyzing consequences of already discussed collision types but in case of colliding with water. Interaction of a high-speed stream of air and vapour and water surface is a point of a specific interest for researchers. Scientists plan to develop more complicated and full models of meteoroid bodies in Earth’s atmosphere.

However, existing techniques for estimating characteristics of a natural cosmic body, while it is on a near-earth orbit, allow quite accurate predictions of its behaviour after entering our planet’s atmosphere.

Source: Science News

Kizilova Anna