In this paper we investigate a hybrid network topology that is suitable for supporting interplanetary communications. We define an architecture comprised of a network of sensor nodes on a remote planetary surface, connected to a hybrid terrestrial network of wired and wireless LANs through a series of satellite relays. All the nodes in the network are IPaddressable and support public and symmetric key cryptography. The resulting network forms a hierarchical hybrid mesh that connects users on Earth to networks on or around a remote planetary surface. We describe the design of the network and present preliminary simulation results illustrating the network performance for various parameters. We also discuss how algorithms for user authentication, message integrity and data confidentiality can be incorporated in the network infrastructure for secure end-to-end communication.