The solar system was originally just a cloud of gas, dust and rocks, which thickened by way of its own gravity. The largest clusters of matter were formed by the gradual collision and packing together of the planet’s material. As the planets grew larger and heavier, more additional material from their surroundings was pulled in by the forces of gravity. Over billions of years, interplanetary space has been pretty well “gravitationally vacuumed”, but there are still plenty of cosmic bodies flying around that pose the threat of collision. There are thousands of asteroids varying in size, hundreds of comets and millions of other projectiles, and endless clouds of space dust.
What falls to earth
Up to 400,000 tonnes of cosmic material falls to earth each year. Most of it is fine dust that burns up in the atmosphere and is seen in the sky as meteors. Only bigger rocks reach the ground and there are tens to hundreds of such meteorites landing every year. Asteroids capable of creating a crater rarely fall to Earth. It is true that the larger the body, the rarer its collision with the Earth (which is good news for us).
The effects of the impact are catastrophic. When it comes to a sudden stop on impact with the Earth’s surface, the projectile transfers all its energy to the rocks it hits within a fraction of a second. Mechanical displacement of the rocks creates an impact crater and pressure transformation of the rocks around the crater takes place. However, most of the energy is transformed into heat energy and causes the melting and evaporation of material.
The consequences of the impact
The consequences could be worse than the blast from a nuclear bomb. In the history of the Earth, it has happened several times that an asteroid of such magnitude has crashed into the planet killing most of the life existing on Earth at that time. Impact craters serve as a reminder to the bombardment of our planet from space, 278 of which have so far been discovered on Earth.