Program: GS-2010B-Q-73

We propose using Michelle to acquire a spatially resolved spectrum of Neptune's central meridian in the Q band (17-25 microns). This portion of Neptune's spectrum is sensitive to temperatures in the 100-400 mbar temperature profile, which we will map as a function of latitude by aligning the slit along Neptune's central meridian. These temperautres wil determine the depth to which extreme radaitive 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. Finally, the radiometry of this spectrum will supplement disk-averaged observations made by Spitzer in the "long-high" mode, which we determined were unusable because of systematic effects. Gemini North/Michelle is preferred because of its prevailing low atmospheric water vapor, but equivalent time will be considered on Gemini South/TReCS with the same low water-vapor requirement.