9816239 Yelle Titan is the object in this solar system with an atmosphere most similar to that of Earth. These atmospheres share similar composition and surface pressures, and we can recognize the same atmospheric regions on Titan that have been defined for Earth. As a consequence, we can learn a great deal by comparing these bodies. Dr. Roger Yelle's investigation is based on comprehensive calculations of atmospheric structure including radiative, dynamical, and chemical processes. The focus is on the upper atmospheres. Results for Earth and Titan will be directly comparable. One outcome should be a better understanding of how the differences in size, gravity, rotation rate, and heliocentric distance affect global circulation. The Titan calculations will be used to interpret Voyager observations of upper atmospheric temperature and composition, allowing answers to questions about the role of dynamics in the thermal structure, or horizontal transport to the chemistry, and the contribution of global wind systems to vertical transport. Funding for this project is shared among the Division of Astronomical Sciences, the Division of Atmospheric Sciences, and the Office of Multidisciplinary Activities in the Mathematical and Physical Sciences Directorate.
