| Description |
We will assess the rotational variability in the stratospheres of the ice giants,Uranus and Neptune, to understand the dynamical and chemical variability of theatmospheric structure of both planets as a function of longitude. This effort followsup observations by the Spitzer IRS that shows consistent evidence for rotationalvariability of stratospheric hydrocarbons in Uranus and intermediate-term variabilityin Neptune.s emissions, neither of whose origins are not well understood. Herschelprovides an opportunity to follow up these observations with its unparalleledsensitivity. Over the 17-hour periods characterizing the equatorial rotation periodsof both planets a series of eight PACS dedicated line scans will be made of strategiclines of HD, methane and water vapor. An efficient scheme takes advantage of thesimultaneous availability of Uranus and Neptune in Herschel.s visibility window. Thesewill assess the variability of hydrocarbons vs temperatures in both atmospheres to anunprecedented accuracy. The results will be analyzed by a team consisting of manymembers of the Key Project on ..Water and Related Chemistry in the Solar System. whowill apply their expertise with the data and its analysis, as well as researchers whodiscovered the Spitzer variability and ground-based inhomogeneity. The data will be examined in the context of models by team members who are experts in radiative transfer, photochemistry, and dynamical modeling of circulation and zonal thermal wave structure. By refining quantitative models for interactions between radiative, dynamical and chemical processes in these two cold but radiatively and dynamically diverse planets, a baseline will be created that will be useful in the interpretation of variability in the spectra of giantexoplanets. This work will also be programmatically useful in the evaluation of thevariability of radiation from Uranus and Neptune, both which are key members of theHerschel flux calibration system. |
