Spitzer Space Telescope - General Observer Proposal #60021


Dynamic Studies of Exoplanet Atmospheres: From Global Properties to Local
Physics

Principal Investigator: Heather A. Knutson
           Institution: Harvard University

     Technical Contact: Heather A. Knutson, Harvard University

Co-Investigators: 
David Charbonneau, Harvard University                                 
Jonathan Fortney, University of California, Santa Cruz                
Adam Showman, University of Arizona                                   
Nikole Lewis, University of Arizona                                   
Eric Agol, University of Washington                                   
Nicolas Cowan, University of Washington                               
Drake Deming, NASA Goddard                                            
Adam Burrows, Princeton University                                    
Greg Laughlin, University of California, Santa Cruz                   
Jonathan Langton, University of California, Santa Cruz                

Science Category: extrasolar planets 
 Observing Modes: IracPostCryoMap 
  Hours Approved: 1138.0 

Abstract:
Spitzer's two-year warm mission represents a unique opportunity to build on its
already-substantial legacy in the area of exoplanetary science with a
comprehensive set of observations that would directly address fundamental
questions about the physical processes that shape exoplanet atmospheres. In our
proposal we outline an exciting two-pronged approach that would combine a survey
of the secondary eclipses for all of the known transiting planets not already
observed during the cryogenic mission with a set of phase curve observations
targeting five of the most interesting objects. The first part of our study
would more than double the number of systems with secondary eclipse observations
and provide the statistical leverage needed to characterize the nature of the
high-altitude absorber responsible for the presence of temperature inversions in
the atmospheres of HD 209458b, TrES-2, TrES-4, and XO-1b. Secondary eclipse
observations alone are not enough, however, as we expect the properties of these
tidally-locked planets may vary substantially between the permanent day and
night sides. Phase curve observations of select systems at several wavelengths
allow us to map out longitudinal variations in the pressure-temperature
profiles, chemistry, clouds, and circulation patterns of these highly-irradiated
atmospheres, and such spatially resolved information will be absolutely critical
in interpreting the results of the broader, low-resolution survey. Comparisons
between the two benchmark systems HD 209458b and HD 189733b as well as a
carefully-selected set of additional planets will allow us to investigate the
importance of irradiation, rotation rate, surface gravity, eccentricity, and
stellar metallicity in determining the pressure-temperature structure and
dynamic meteorology of these atmospheres. We are requesting a total of 1138
hours for these observations.