The lander and the airbags protect the rover from the impact of landing. The beams and sheets of the lander are made out of composite materials.
This makes the lander strong and lightweight. The lander beams are made out of carbon-based layers of graphite fiber woven into a fabric, creating a material that is lighter than aluminum and more rigid than steel. Titanium fittings are bonded (glued and fitted) onto the lander beams to allow it to be bolted together. The Rover is held inside the lander with bolts and special nuts that are released with small explosives after landing.
The lander consists of a base and three sides "petals" in the shape of a tetrahedron. The three petals are connected to the base of the tetrahedron with hinges. The hinge has a powerful motor associated with it. This motor can lift the weight of the entire lander. This is because of the lower gravity on Mars
The Rover has accelerometers (sensors) that can sense their position with respect to the Martian surface by measuring gravity. Due to this, the correct lander petal can be commanded to open. Once the base petal is down and the rover is upright, the other two petals are opened.
If the petals while opening encounter a rock, the middle petal and the rover will be held in place and will be raised to a height over the surface till the three petals are parallel to the ground and are flat. Commands may then be sent from earth to adjust the petals to create a better pathway for the rover to drive safely off of the lander and go onto the Martian surface without encountering a steep fall.
The lander petals contain a retraction system, which drags the deflated airbags away from the rover and towards the lander. About 3 hours is allotted to retract the airbags and deploy the lander petals.
We have seen the different instruments which help in landing, let us now see the operations that have to be performed during landing.