The parachute is located ion the back shell part of the spacecraft.
The design of the parachute depends upon the forces, which the parachute experiences when it is fully inflated. These forces are called as loads. Loads depend upon atmospheric density, velocity, parachute drag area, and mass. The load for the Mars Exploration Rover is between 18,000 and 19,000 pounds.
The parachute is made out of polyester and nylon. The parachute has three tethers connecting it to the back shell (bridle), of Kevlar.
These materials are used since they are:
They are strong
They are lightweight
We can fit them inside a very small area by pressure packing.