Mars Science Laboratory is a scientific mission to the surface of Mars that would include a rover with 10 science instruments. In order to accomplish this mission, the rover must be transported from Earth to the Martian surface. The mechanical hardware that transports the rover is developed by the Cruise, Entry, Descent, and Landing (CEDL) Mechanical Subsystem Team. This mechanical hardware includes the Cruise Stage Structure, the Aeroshell Subsystem, the Parachute Deceleration Subsystem, the Descent Stage Structure, the Bridle & Umbilical Device, and the pyro and separation devices that allow for the numerous separation events that occur in the EDL sequence.The key challenges for this system lie in the complex configuration (both geometric and subsystem accommodations), multiple unique load cases, and numerous separation events. This paper will describe the preliminary design and key challenges of each of these mechanical assemblies that comprise the CEDL Mechanical Subsystem. 12