As part of an envisioned autonomous swarm exploration mission in Valles Marineris on Mars a design investigation of a high-range scout UAV is performed in this work. Two VTOL configurations, a coaxial helicopter and a transition tailsitter, are examined to assess their suitability. A preliminary design framework using Python and the optimization framework OpenMDAO is created using the preliminary design software NDARC. To model the rotor performance, comprehensive analysis simulations are executed using CAMRAD II. Structural 2D-FEM beam models are created for the rotor blades and the wing for weight modeling. Design sizings are executed for operation in the extremely thin atmosphere and the mission performance for a scouting mission as part of the robotic Valles Marineris Explorer (VaMEx) swarm is examined. A behavioral model is created to evaluate the controllability of the configurations. The results for a mission with a cruise flight of 30 km and 1.4 kg of payload show that for such a mission the transition configuration does not offer advantages over a more conventional coaxial helicopter design. To understand design sensitivities and to evaluate the respective effects on vehicle performance parameter sweeps are conducted.