“As of October 2016, all methods of landing on Mars have required an aeroshell and parachute sequence for Mars atmospheric entry and descent, but after that there are three choices. A stationary lander can drop from the parachute back shell and ride retrorockets all the way down, but a rover cannot be burdened with rockets that serve no purpose after touchdown.
One method (for lighter rovers) is to enclose the rover in a tetrahedronal structure which in turn is enclosed in airbags. After the aeroshell drops off, the tetrahedron is lowered clear of the parachute back shell on a lanyard so that the airbags can inflate. Retrorockets on the back shell can slow descent. When it nears the ground, the tetrahedron is released to drop to the ground, using the airbags as shock absorbers. When it has come to rest, the tetrahedron opens to expose the rover.
If a rover is too heavy to use airbags, the retrorockets can be mounted on a sky crane. The sky crane drops from the parachute back shell and, as it nears the ground, the rover is lowered on a lanyard. When the rover touches ground, it cuts the ...