Energy conversion

See meteor shower on youtube
The surface of the Moon is full of craters as there is no atmosphere to protect itself from meteors. The loss of gravitational potential energy as an object falls from space must be converted to other forms of energy namely kinetic energy and heat energy. Atmosphere produces resistive force than in turn causes work to be done against it hence producing heat energy. This will limit the further increase in velocity as resistive force increase rapidly with velocity. The temperature of the object gets so high that the material just vaporises. By the time the object reaches the surface of the Earth it would have disappeared in the air , saving us from being hit . Now and again we do hear of falling objects from the sky but so far no fatality. The Moon is not so fortunate and therefore its surface is marked with craters. See link to the map of the Moon