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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
For more information, click on any of the tabs at the top or bottom of the page.
Click here for FAQ about global warming.
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