Why are all craters round?


There are many craters in our solar system. There are more of them on some celestial bodies, as on the Moon or Mercury. On others, less (on Earth). However, what all craters have in common is that almost all of them have a round or close to round shape.

At first glance, the shape of the crater should depend on the angle at which the collision occurred, and it is statistically impossible for all collisions of celestial bodies in the solar system to occur at right angles. Let’s figure out what the reason is.

In fact, there is nothing strange about the fact that most of the craters have a shape close to a circle. This has to do with how craters are formed. The notion that a crater is a dent from a meteorite impact is not entirely true.

When a meteorite hits a celestial body, a huge amount of energy is released. For example, the power of the explosion of the Chelyabinsk meteorite was about 500 kilotons in TNT equivalent, which is about 20 times higher than the power of the bomb dropped on Hiroshima. Fortunately, the explosion took place high in the atmosphere and no people were injured.

When a meteorite reaches the surface in the form of one piece, the explosion occurs on the ground and the released energy, the formation of the crater walls occurs precisely as a result of the explosion and the scattering of the soil by the shock wave in different directions, and not from the “pushing” of the soil by the meteorite body.

The crater is always hundreds of times larger than the meteorite that led to its formation. For example, the famous Berringer Crater in Arizona, which is approximately 1200 meters wide, was formed by the fall of an approximately 50-meter meteorite.

The crater can be elongated only if the fall occurs tangentially. It is believed that for an elongated crater to form, the collision angle must be less than 8 degrees. There are no such craters on Earth, but there are on the Moon (Messier crater), Mars (Pater Orc) and other celestial bodies.

However, there are craters and completely bizarre shapes. So the Berringer Crater in Arizona, already mentioned in this article, is closer in shape to a square than to a circle. Usually, this shape of craters is due to the geological structure of the surface of the celestial body where the meteorite fell.