The collision in a system whose momentum is conserved can be categorized as either elastic or inelastic, based on the nature of the interaction. A collision that leads to a decrease in the system's kinetic energy is termed an inelastic collision. For instance, consider a collision between two asteroids. During the collision, the system constituted by the two asteroids may lose some of its kinetic energy as heat and light. In case of a perfectly inelastic collision, however, the colliding objects suffer a maximum loss in kinetic energy and unite, resulting in the final kinetic energy of the system to become zero. If a meteorite hits the Earth’s surface and comes to rest after the collision, then it is said to have lost all its kinetic energy while forming a crater on the surface. This also means that the particles constituting the system, the meteorite and the Earth, would stay together after the collision. A collision in which the kinetic energy of a system increases is termed an explosion. For example, during a firecracker explosion, the chemical potential energy is converted to kinetic energy.