Mars Atmospheric Radiation Imaging Orbiter (MARIO) is a 16U stand-alone CubeSat mission that shall escape Earth, perform autonomous deep-space cruise, achieve ballistic capture, and enter an operational orbit at Mars to perform thermal radiation imaging. This work focuses on the systems design of MARIO. The design of combined chemical-electric propulsion systems, comprising FLP-106 based green chemical monopropellant thruster and the iodine-fueled RF ion thruster, for hybrid high-thrust-low-thrust Earth-Mars transfer is presented. Reflectarrays along with high-gain antennas are utilised to establish long-distance low-bandwidth X-band communication link with the Earth. Electrical power system design is pursued to provide steady power to the system during the transfer and science operations phases. A novel autonomous navigation strategy is proposed which includes horizon-based optical navigation near target bodies and deep-space line-of-sight navigation for accurate state estimation for autonomous operations. Details regarding on-board processing, attitude determination, and thermal control are delineated. Feasible budgets for mass and communications link are obtained. The structural composition of MARIO is detailed.