HR: 0800h
AN: P51B-1430    [Abstracts]
TI: Laboratory Studies of Ammonia Ices Relevant to the Jovian Atmosphere
AU: Meharchand, R T
EM: rtm02@garnet.acns.fsu.edu
AF: Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025 United States
AU: Meharchand, R T
EM: rtm02@garnet.acns.fsu.edu
AF: Present Address: Florida State University, Department of Physics, Tallahassee, FL 32306 United States
AU: Boulter, J E
EM: boulteje@uwec.edu
AF: Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025 United States
AU: Boulter, J E
EM: boulteje@uwec.edu
AF: Present Address: University of Wisconsin-Eau Claire, Department of Chemistry, Eau Claire, WI 54702 United States
AU: Baer, C E
EM: cbaer@wellesley.edu
AF: Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025 United States
AU: Baer, C E
EM: cbaer@wellesley.edu
AF: Present Address: Wellesley College, Department of Physics, Wellesley, MA 02481 United States
AU: * Kalogerakis, K S
EM: ksk@sri.com
AF: Molecular Physics Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025 United States
AB: Ammonia ice condensation and cloud formation microphysics are topics of relevance for understanding the atmospheres of the giant planets. Ammonia ices are also considered important components of the icy satellites found in the outer solar system, and are thought to play an important role in their geological activity. Although observational evidence and thermochemical models suggest ammonia clouds in the Jovian atmosphere should be ubiquitous, less than only 1% of Jupiter$'$s atmosphere appears covered by spectrally identifiable ammonia clouds, with a clear preference in turbulent regions.$^{1,2}$ The paradox of the rather scarce spectroscopic signatures of ammonia clouds and their appearance in turbulent regions suggests that the nascent ammonia clouds may undergo processing that modifies their spectroscopic properties. No relevant laboratory experimental results are available to resolve this problem. Two possible sources of processing that have been suggested in the literature include photochemical solid-state modification ($''$tanning$''$) and coating of ammonia particles by other substances present in the stratospheric haze.$^{2,3}$ We are performing laboratory investigations with the objective to provide information on the photophysical and chemical processes that control the optical properties of the Jovian ammonia clouds. In the experiments, thin ice films of ammonia are coated with organic molecules, such as saturated and aromatic hydrocarbons, and characterized by infrared spectroscopy. Preliminary results indicate suppression of the ammonia absorption feature at 2.7 $\mu$m by a thin layer of hydrocarbons. The implications for the spectral signatures of ammonia clouds in the atmospheres of Jupiter and Saturn will be discussed. Funding from the NSF Planetary Astronomy Program under grant AST-0206270 is gratefully acknowledged. The participation of Rhiannon Meharchand and Christina Baer was made possible by the NSF Research Experiences for Undergraduates Program under grant PHY-0353745. 1. S. K. Atreya and A.-S. Wong, Eos. Trans. 84(46), Fall. Meet. Suppl., Abstract A12A-0072 (2003), and references therein. 2. K. H. Baines, R. W. Carlson, and L. W. Kamp, Icarus 159, 74 (2002). 3. A.-S. Wong, Y. L. Yung, and A. J. Friedson, Geophys. Res. Lett. 30, 1447 (2003).
DE: 5799 General or miscellaneous
DE: 6220 Jupiter
DE: 6299 General or miscellaneous
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting