We are all familiar with seasonal effects on Earth; they are observed in our living environment, in the stratosphere, the ionosphere and beyond. Seasonal effects are also at work on other bodies of the solar system as revealed by remote sensing instruments or in situ probes/rovers. Seasonal variability is currently well studied on Mars where processes such as the formation of CO2 frost on the south polar cap or the condensation of H2O on both polar caps are now well understood. Thanks to long-term observations by Cassini-Huygens, the Saturn system is proving to be a rich laboratory for studying seasonal variations in a variety of environments. In particular, several seasonal effects are investigated in the highly complex Titan system, on its surface, in the surface/atmosphere interaction, and in all its atmosphere/ionosphere layers. It is worth mentioning the apparition of equatorial storms at the equinox, and the formation of mid-latitude clouds in the southern hemisphere during winter concurrently monitored by Cassini-Huygens instruments and complementary long-term ground-based observations of the Saturnian moon. At Rhea and Dione, Cassini observations point to seasonal O2-CO2 exospheres and possible seasonal frosts. The Cassini mission also shows seasonal variations in the interaction between the atmosphere/ionosphere of Saturn's rings, which in turn are causing seasonal variations in the water flux in Saturn upper atmosphere and in the magnetospheric O2+ density. Earth-based telescopes allow to study remotely seasonal variations in Uranus and Neptune atmospheres and on Pluto and its main satellite Charon.

Observations, their interpretation, and modelling work related to sessional variability across the solar system are topics relevant to this session, which goal is to highlight the common physical and chemical phenomena that govern seasonal effects in the solar system. We will also discuss the benefit of the study of the same processes on Earth.

This session will include solicited keynote reviews and oral and poster contributions.