Because of the scientific challenges of space explorations, several space agencies are involved in the design of autonomous planetary surface exploration devices. Examples are Mars rovers, designed with the goal of collecting terrain information, including dust, soil, rocks, and liquids. The design of such sophisticated rovers can be enhanced by less reliance on trial-and-error process, building expensive physical models, and time-consuming experimental testing. Physics-based virtual prototyping is necessary for an efficient and credible Mars rover designs. In this thesis, a new flexible multibody system (MBS) rover model for planetary exploration is developed. Because the rover, a wheeled robot, must be designed to negotiate uneven terrains, the airless wheels must be able to adapt to different soil patterns and harsh operating and environmental conditions. In order to describe accurately the airless-wheel complex geometry and capture its large deformations and rotations, the absolute nodal coordinate formulation (ANCF) finite elements are used. A numerical study is performed to compare the ANCF kinematics and tractive force results with the results of the discrete brush tire model, widely used in the vehicle-dynamics literature. Several simulation scenarios are considered, including a drop test and acceleration along a straight line. The numerical results obtained are verified using data published in the literature and are used to evaluate the accuracy and computational efficiency of the ANCF airless-tire modeling approach.