Talks My specific research experience with Jupiter's clouds--and the gases that form them--also relates to conditions in the early protoplanetary disk and dynamics of giant planet atmospheres. The interaction between photochemistry and clouds in the atmospheres of Jupiter and Titan may also provide an avenue for investigating processes leading to the synthesis of complex organic molecules in planetary atmospheres, including the atmosphere of the early Earth. The talks below organize my research into overarching themes in the science of planetary atmospheres. The talks can be geared towards audiences at the levels of Jupiter specialists, general planetary scientists, or the general public. I can also be booked to speak for a seminar or colloquium through JPL's Outer Planets Colloquium Series.
	RED SPOT JR. AND JUPITER'S GLOBAL UPHEAVAL White Oval BA turned red, like the Great Red Spot, in late 2005. Collaborator Chris Go, an amateur astronomer in Cebu City, Philippines, was the first to note this color change. But the story really begins in the 1920s, when Jupiter suffered a planet-wide disturbance called a "global upheaval." Three White Ovals formed after this upheaval, and coexisted happily at the latitude of 33° south, until they began merging together in 1998. By 2001, only a single oval remained: Oval BA. When this feature turned red, astronomers nicknamed it "Red Spot Jr." or the "Little Red Spot." While the how and why of the color change are hotly debated in the planetary community, our group and others are continuing to acquire an exciting array of Hubble and ground-based imaging and spectroscopic data to provide answers to these questions. Collaborator Phil Marcus made an interesting prediction in 2001 after studying the merger of the three white ovals. He believed that the merger would lead to a shutdown of heat transfer from the equator to the pole across the latitude of 33° south. The buildup of equatorial heat would lead to new phenomena in Jupiter's atmosphere. Indeed, about 7 years after the merger (one radiative timescale), Oval BA turned red. The following year, in 2006, Jupiter began a new global upheaval, producing effects that are already helping us better understand the Jovian atmosphere.
	OUTER PLANET VOLATILE ABUNDANCES This talk is structured around the exploration of several intimately related questions concerning water and other volatiles in giant planets: What is the cloud structure in the giant planets? What did the Galileo Probe Mass Spectrometer find out about water on Jupiter? Have remote sensing efforts measured water in the giant planets? Will remote sensing succeed in the future? Can the abundances of other volatiles indirectly tell us about water? How do volatile abundances compare among the giant planets? What do the densities of giant planet moons tell us about their origins? Can we use giant planet volatile abundance ratios to constrain how the planets formed, and also characterize the icy planetesimals that contributed to their formation? What conditions would permit oceans to exist in ice giant planets?
	NITROGEN ON JUPITER - CLOUDS AND COSMOCHEMISTRY Three different gases condense in Jupiter's troposphere, resulting in a complex vertical distribution of clouds. Water forms the deepest of these clouds, but water clouds are usually obscured by overlying cloud layers. The layer above, probably composed of ammonium hydrosulfide, results when highly toxic ammonia and hydrogen sulfide gases react to form a solid. The chemistry of this strange cloud layer is poorly understood, partly because of the hazards of working with these gases in the laboratory. Ammonia itself condenses in Jupiter's cold upper troposphere, yet the distinct spectral signatures of ammonia ice are surprisingly uncommon. Small ammonia cloud particles may be wafted upward to contribute to the thin haze that blankets the planet above the clouds. Since cloud heights, cloud thicknesses, and ammonia gas concentration are variable on Jupiter, we use them to trace dynamic processes in the atmosphere. The elements N and S (and probably O) in Jupiter's cloud-forming gases are about four times more enriched (with respect to hydrogen) than in a protosolar composition gas. Carbon and noble gases are also enriched. It is generally believed that these elements were enriched when Jupiter accumulated icy planetesimals during its formation, but planetesimals with the necessary abundance ratios have never been observed. The origin of these planetesimals (and therefore Jupiter itself) is still a mystery.