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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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