A laner is a spacecraft which descends toward and comes to rest on the surface of an astronomical body. For bodies with atmospheres, the landing is called re-entry and the lander descends as a re-entry vehicle. In these cases landers may employ aerobraking and parachutes to slow down, often with small landing rockets which fire just before impact to bring the lander to rest relatively gently. The Mars Pathfinder mission also used inflatable airbags to cushion the lander's impact. When a high velocity impact is planned, the spacecraft is called an impactor.