Abstract—Planetary scientists are greatly interested in the caves present on the Moon and Mars, however these areas present major challenges to current space robots. A new space robotics concept, Microbots, is presented and a possible reference mission to Mars is discussed. The feasibility of the mobility and power systems of the Microbot are analyzed within the context of the reference mission. The results of this analysis are that the Microbot system is a feasible concept for a development timeline of approximately 10 years. I. INTRODUCTION here is an important scientific motivation to explore the extraterrestrial (ET) caves of the solar system, including the Moon and Mars [1]. These caves possibly contain water deposits, biological materials, as well as significant geological and geomorphologic information. Hence, there is significant interest in exploring extraterrestrial caves in future space missions [2]. Figure 1 shows a Martian lava tube cave with collapsed roof sections known as skylights. Astronaut exploration of ET caves would be exceedingly dangerous and therefore such missions are a strong candidate for robotic or combined astronaut-robot exploration. Current exploration robot designs, such as the Mars Exploration Rover (MER) and the Mobile Science Laboratory (MSL) are not well suited for subsurface exploration. These robots are unable to traverse extremely rough terrain, navigate over large obstacles, or ascend and descend very steep slopes. Rough terrain entrapment of such systems would result in single point mission failure. Hence, mission planners are unlikely to risk a rover in unknown subsurface area such as a cave. Manuscript received September 15, 2006. This work was supported by the NASA Institute for Advanced Concept (NIAC). S. B. Kesner, J.S. Plante, and S. Dubowsky are with the Massachusetts Institute of Technology, Cambridge, MA 02139 USA (617- 253-2144; fax: 617-258-7881; e-mail: dubowsky@mit.edu) P.J. Boston is with the New Mexico Institute of Mining and Technology, Socorro, NM 87801 USA (505-835-5657; fax: 505-835-6436; email: pboston@nmt.edu) T. Fabian is from Stanford University, Stanford, CA 94305, USA (650-723-7629; Fax: 650-723-5034; email: tfabian@stanford.edu) This paper describes a robotic ET exploration concept to deploy hundreds or thousand of small and sacrificial ball- like robots onto the surface of Mars. These robots would explore subsurface lava tubes, entering through cave skylights. They could be deployed from an orbiter with a balloon landing, such as were used by the MER rovers Spirit and Opportunity (see Figure 2). They could also be dropped or thrown into cave openings by astronauts or carried by conventional rovers. These mobile robots, or “Microbots,” would be self-contained spherical devices approximately 100 millimeters in diameter with a mass of approximately 100 grams (see Figure 3). Microbot would contain a micro fuel cell power system, communication and data processing equipment, a payload of scientific and navigation sensors, and a Dielectric Elastomer Actuator (DEA) mobility system that produces a combination of hopping, bouncing, and rolling. Preliminary analysis has shown that a mission of two thousand Microbots would have the same launch weight and volume as a single MER rover. This paper presents a feasibility analysis of the Microbot system design for a 10 year development timeframe. The system performance is evaluated in the context of a reference mission to Mars. The operation and efficiencies of the Microbot subsystems are discussed, focusing on the power and the mobility subsystems. II. SYSTEM CONCEPT The Microbot system is an exploration robot designed to traverse very rough terrain while being robust to single point failures. After deployment, the Microbots would use their mobility systems to hop, bounce, and roll over the planet’s surface in the direction of a feature of interest, such as a cave entrance, a deep ravine, or a canyon. This mobility strategy is an effective option for low gravity environments, such as Mars and the Moon [3]. Mobility and Power Feasibility of a Microbot Team System for Extraterrestrial Cave Exploration Samuel B. Kesner, Jean-Sébastien Plante, Penelope J. Boston, Tibor Fabian, and Steven Dubowsky T 25 km Skylight Sections Fig. 1. An orbiter view of a lava tube cave with skylights on Mars. Fig. 2. The Microbot exploration concept showing orbiter deployment. 2007 IEEE International Conference on Robotics and Automation Roma, Italy, 10-14 April 2007 FrE10.1 1-4244-0602-1/07/$20.00 ©2007 IEEE. 4893