It is a general understanding that, in order to answer such questions considering the so called planetary habitability, next to the theoretical research, we need concrete planetary missions, which explore and investigate the planetary bodies within our Solar System from the orbit via Remote Sensing, but also in-situ on the planetary surfaces. The department of Exploration Systems at the Institute of Space Systems investigates, in the framework of the HGF-Alliance, advanced methods, tools and strategies for such exploration missions. Of special interest is the design of advanced mission concepts, which will investigate so far unexplored regions within our Solar System. Such regions, for example the polar regions on Mars, potential subsurface aquifers or the so called gullies, i.e. channels that potentially hint to subsurface liquid water, may have the pre-requisites to bear signs of extant of extinct life. Furthermore, we are also seeking for innovative solutions to explore the subsurface ice layers and oceans on the outer planet moons, for example using melting probes and underwater robotic systems.