Mobile robots are of high interest for unmaned planetary exploration. The very successful Pathfinder mission to Mars has impressively demonstrated the potential of mobile platforms for planetary exploration [1]. The European Space Agency (ESA) also started to develop concepts for micro-rovers for Mars missions. Within an interdisciplinary group of companies specialized in space applications and research labs new designs of micro-rovers have been investigated. Two concepts, a simple and robust one and an innovative one, have been selected and functional breadboard models of them are currently built. After a discussion of the key issues for robust locomotion the present paper will focus on the design and control of the more innovative solution. It consists of 6 independently driven wheels arranged in two triangles. It therefore allows not only for efficient rolling on flat surfaces but also to step on obstacles. Additionally the center of mass and the instrumentation carrousel is adjustable, allowing to optimally balance the micro-rover in almost every situation. Even after flipping over the robot will always be able to get back on its wheels.