Sky crane is a soft landing system used in the last part of the entry, descent and landing (EDL) sequence developed by NASA Jet Propulsion Laboratory for its two largest Mars rovers, Curiosity and Perseverance. While previous rovers used airbags for landing, both Curiosity and Perseverance were too heavy to be landed this way. Instead, a landing system that combines parachutes and sky crane was developed. Sky crane is a platform with eight engines that lowers the rover on three nylon tethers until the soft landing.
EDL begins when the spacecraft reaches the top of the Martian atmosphere. Engineers have referred to the time it takes to land on Mars as the "seven minutes of terror."[1]