The structures subsystem is the skeleton around which the spacecraft is assembled. It supports and protects the other engineering subsystems and the science instruments. It was strong enough to survive forces in excess of 5 g's during launch. To do this, the structure had to be designed as if the spacecraft weighed five times its actual weight on Earth! Extremely lightweight but strong materials, including titanium, carbon composites, and aluminum honeycomb, provided the structures with the necessary strength.