John J. Caldwell Ph.D. (Wisconsin) Professor of Astronomy This e-mail address is being protected from spambots. You need JavaScript enabled to view it Research Field: Planetary Physics Research specialization: Space astronomy; planetary astronomy, extra-solar planets. Publications

My research is primarily, but not exclusively, related to observations made with the Hubble Space Telescope (HST). Past and continuing research has been concentrated on the atmospheres of planets and satellites. Planetary studies have included atmospheric composition, haze and cloud effects, and aurorae.

Future topics to be addressed include planetary lightning, and the influence of Raman scattering on spectra. Among the planets, the emphasis has been on the gas giants. Of the satellites, Titan has received the most attention, followed by Io. Titan is particularly interesting because its atmosphere is unique among satellites in the solar system, having a column abundance ten times greater than that of planet Earth, and a distinctive composition including numerous hydrocarbon and nitrile molecules. There are also condensate cloud layers and high altitude hazes, the latter probably of photochemical origin. Titan exhibits clear seasonal effects, manifested in hemispheric brightness asymmetries, although the dynamics of the atmosphere have been essentially not observed in detail.

A developing interest is the study of extra-solar planets. Many recent discoveries have demonstrated that such objects do exist. To date, the discovery method has exclusively been precise, high resolution Doppler spectroscopy to measure the reflex motion of the parent stars due to the small but significant gravitational pull of the planets' masses. We participate in complementary techniques, including attempts to image planets and other stellar companions directly with the Hubble Space Telescope.

For the academic year 1998-99, Professor Caldwell was on sabbatical leave at the NASA Ames Research Center. There, he was working with a science team that is developing a mission known as Kepler, which has the goal of discovering Earth-like planets around other stars. The interest in Earth-like planets, as opposed to the larger, Jupiter-like ones that have already been discovered, is driven by the probability that such planets are the best natural environment for the evolution of life.