Saturn Atmospheric Science in the Next Decade

Although observed from the Earth, Pioneer 11, Voyagers 1 and 2, and now Cassini in its primary and 2-year extended mission, the characterization of fundamental atmospheric properties and processes in Saturn remains incomplete. Many open questions about the atmosphere could be addressed in the next decade:

- SEASONS: How do seasons affect (a) the global distribution of gaseous constituents and aerosols; and (b) temperatures and the stability against convection and large scale-atmospheric transport? Will a warm polar vortex appear at the northern pole with greater radiative input?

- HEXAGON: What is the vertical structure of the hexagon, what is driving and maintaining it; and why is there no feature of similar longevity at the south pole?

- COMPOSITION AND CHEMISRY: What are the noble gas and oxygen abundances? What is the relation of stratospheric hydrocarbon distributions to radiative climate influences and photochemistry? What is the rate of influx of ring and other exogenic materials into the atmosphere?

- CLOUDS AND HAZES: What is the tropospheric cloud inventory, and what are the different cloud compositions and optical properties? What is producing the haze material? What is the relation between observable clouds and lightning discharges? What is the relation between the fine-scale cloud structure identified at 5 microns and the

distribution of condensates, such as ammonia? Do 5-micron clouds have counterparts at other altitude levels?

- DYNAMICS: What is the source of the strong equatorial upwelling and strong prograde jet? What changes when we see the emergence of Great White Storms? How is energy transported by waves between atmospheric levels, via the SAO and by vertical waves observed in stellar occultations and RSS profiles? What effect does the ephemeral nature of Saturn's slowly-moving thermal waves have on the atmosphere? Will the tropospheric hotspots at each pole persist?