Establishing reliable and direct communications links from Earth to Mars rovers, also known as Direct-to-Earth (DTE) communications, is a complex and challenging antenna design problem. The possibility of diminished UHF relay assets for the upcoming Mars 2020 mission requires a high performance antenna array system to enable substantial return of valuable scientific data. This thesis examined various element geometries and subarray architectures, including developing a feasible power dividing stripline network. After this comprehensive examination, a novel lightweight and low-profile X-band single feed circularly polarized antenna subarray comprised of half E-shaped elements is proposed. The proposed design was simulated, prototyped, and measured, showing good agreement between simulation and measurements. The design is also robust, shown by various sensitivity analysis such as the effect of fabrication tolerances. Through this novel design, the challenging NASA DTE system level requirements can be achieved.