Planetary Environments: Scientific Issues and Perspectives

LESIA, Observatoire de Paris, CNRS, 5 place Janssen, 92195 Meudon, France

Abstract

What are the planetary environments where conditions are best suited for habitability? A first constraint is provided by the presence of liquid water. This condition allows us to define two kinds of media: (1) the atmospheres of solid (exo)planets with a temperature typically ranging between 0°C and 100°C, and (2) the interiors of icy bodies (outer satellites or possibly exosatellites) where the pressure and temperature would fit the liquid phase region of the water phase diagram. In the case of Mars, significant progress has been achieved about our understanding of the history of liquid water in the past, thanks to the findings of recent space missions. The study of the outer satellites is also benefiting from the on-going operation of the Cassini mission. In the case of exopl nets, new discoveries are continuously reported, especially with the Kepler mission, in operation since 2009. With the emergence of transit spectroscopy, a new phase of exoplanets’ exploration has started, their characterization, opening the new field of exoplanetology. In the future, new perspectives appear regarding the exploration of Mars, the giant planets and exoplanets, with the ultimate goal of characterizing the atmospheres of temperate exoplanets.