Exploring the satellites of the outer planets with in situ elements

The exploration of the systems of the outer planets of the Solar System, in particular Jupiter and Saturn, is in the forefront of contemporary space exploration. Indeed, these two planetary systems host extreme environments which can provide us with information on the origin and evolution and the interactions therein. The major satellites of these gas giants, like the Jovian Europa, Ganymede, Callisto, and Io, as well as the Kronian Titan and Enceladus, harbor geophysically and astrobiologically interesting conditions which sometimes resemble terrestrial procedures, albeit with a vast combination of different materials and thermodynamic parameters. Following the legacy of the Cassini/Huygens mission, the Titan Saturn Space Mission (TSSM) has been proposed and selected for further study as a large class mission consisting of an orbiter, a hot air balloon and a lake-lander and it is designed to offer a long-term full close up and in situ coverage of both Titan and Enceladus [1]. Recently selected within the NASA Discovery program is the Titan Mare Explorer (TiME) which plans to land a probe in one of Titan´s lakes and explore its composition [2]. A complementary proposal for Saturnian exploration is the Titan Aerial Explorer (TAE) which includes a high-pressure Helium balloon with the capability for ground-penetrating radar, radio science and multi-spectral imaging and spectroscopy, focusing on the study of Titan´s atmosphere and surface [3]. Finally, the Europa Jupiter System Mission (EJSM) is composed of an orbiter destined to study extensively the Galilean Satellite Ganymede, Jupiter´s magnetosphere and the interactions among the satellites [4]. The study of these intriguing planetary bodies not only gives us the opportunity to exceed our knowledge concerning this space area, but also to experiment in planetary scale laboratories with a host of new, state-of-the-art instruments.