Program: GS-2007B-Q-47

We propose to determine the vertical extent of strong radiatively and dynamically driven thermal anomalies in Neptune's atmosphere which we discovered at the VLT in September, 2006. Our proposed observations will enable us to measure the depth of seasonal forcing in Neptune, infer the general circulation of its atmosphere, and assess the lifetime of compact, hot areas of its stratosphere. There are three components to our observations. (1) A Q-band spectrum along Neptune's central meridian is sensitive to the 100-400 mbar temperature profile vs latitude, determining the depth to which extreme radiative seasonal warming of Neptune's 100-mbar tropopause at the south pole extends down into the convective region. It will also measure Neptune's para-H2 fraction vs latitude, providing a tracer of vertical motions. (2) An N-band spectrum along Neptune's central meridian will measure emission from stratospheric CH4 and other hydrocarbons vs latitude. The strength of these gradients from Neptune's south pole, where methane is leaking into the stratosphere, will determine the rate of latitudinal transport and hydrocarbon production in the stratosphere. (3) Images of opposite hemispheres at 7.7, 8.7 and 12.3 microns will determine whether a high-latitude stratospheric hot spot detected in VLT images at 8.6 microns (CH4) and 12.3 microns (C2H6) last September persists. These spatially resolved results will provide an important level of realism to our disk-averaged Spitzer spectra of Neptune. This proposal is for Gemini S and uses Gemini S for all but the Q-band spectroscopy, which is better done at Gemini N.