|A new frame for a new diorama.|
The MSL (Mars Science Laboratory) is a much bigger endeavour than the previous two missions to Mars' surface were. Sojourner just was a rover the size of a medium-sized radio-controlled toy car, just 65 cm long. Its successors, the MER-twins Spirit and opportunity, were double sized, measuring one and a half meter in length. Curiosity again is twice as big, it has the size of a small car, being 3 meters long. So while the other rovers could be dropped on a parachute, covered in a coat of balloons to break their fall, they had to come up with something else for Curiosity, being so much heavier.
Enter Sky Crane. A robot which is not supposed to land but to break the fall of Curiosity and hover over the ground at a height of 7,5 meters. The rover is winched down on three cables and when the wheels touch the ground, the cables will be severed and the Sky Crane will fly away in a large arc and crash at a safe distance of the rover.