Kessler belts are debris fields that orbit a planet. They are caused by Kessler Syndrome events in which colliding satellites create dangerous debris which in turn destroy additional satellites in a cascade that eventually generates an impenetrable (or nearly impenetrable) field of orbiting junk surrounding a planet. Spaceships that wish to land on or depart from the planet surface must fly through the Kessler belt and risk being destroyed by the debris (which would only add to the cloud). Kessler fields may contain derelict ships and damaged ships. They may also be caused by the destruction of an orbital ring. Fictional Kessler belts may have hidden routes through them that can be successfully navigated.