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Professor Adam Showman

(Adam Showman)
Lunar and Planetary Lab
University of Arizona
Tucson, AZ 85721-0092

Office: Space Sciences 432
Phone: (520) 621-4021
Email: showman and then "at" and then lpl.arizona.edu

Dr. Showman investigates the dynamics and evolution of planetary atmospheres and interiors. His atmospheric research currently focuses on giant planets -- Jupiter, Saturn, Uranus, Neptune, and the hundreds of giant planets that are being detected around other stars. Sunlight absorption and heat loss cause the weather in all these atmospheres, but the outcomes on different planets are diverse, depending on the strength of the solar heating, the presence or absence of dust and cloud-forming gases, the rotation rate, and other properties. The giant planets in our solar system have winds up to ten times stronger than Earth's despite much weaker solar heating. Specific questions include: what controls the depth and strength of the jet streams in these bottomless atmospheres? What powers the hundreds of hurricane-like vortices that exist, and how do these vortices interact with the jet streams? What is the role of water vapor, which is known on Earth to play a key role in shaping the circulation? For extrasolar planets, we are in the midst of a revolution in characterizing the so-called "hot Jupiters" -- giant planets that are up to 20-30 times closer to their stars than Earth is to the Sun. Blasted by starlight, these tidally locked planets occupy a regime unseen in our solar system. Radii, densities, atmospheric compositions, dayside spectra, and even infrared lightcurves constraining the day-night temperature patterns are being determined from Spitzer Space Telescope, Hubble Space Telescope, and groundbased observations. Dr. Showman's research in this area seeks to understand the atmospheric circulation on these exotic objects, with the goal of explaining current and future lightcurves, spectra, and other observables. The fundamental goal is to broaden our knowledge of atmospheric dynamics beyond the boundaries familiar from our solar system.

Dr. Showman's interior research focuses primarily on the icy satellites of the outer solar system. Europa, Ganymede, Enceladus, Miranda, Ariel, and other moons display a diverse assortment of grooves, ridges, rift valleys, disrupted "chaos" regions, and possible cryovolcanic structures that are alien from a terrestrial perspective. What caused these terrains? Why are some moons (Europa, Ganymede, Enceladus) heavily reworked while others (Callisto, Rhea, Mimas) relatively dead? How do the geological/geophysical processes differ from those on Earth? What is the role of tidal heating and flexing (which is unimportant on Earth but crucial on many icy satellites)? Under what conditions can convection in the satellite interior lead to surface disruption? How are the geologic histories influenced by the orbital histories and vice versa? And what is the surface-atmosphere interaction in the smog-shrouded atmosphere of Saturn's largest moon, Titan? These are among the questions under investigation.

In addition to the active research areas described above, Dr. Showman also has a long-term interest in the atmospheric dynamics, climate, interior state, and geophysics of the terrestrial planets Earth, Mars, and Venus.

Press release on Jovian jet streams

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