P53A-4002:
The Spatial Distribution of Radiated Endogenic Power from Enceladus' South Polar Region
Friday, 19 December 2014
John R Spencer, Southwest Research Institute, Boulder, CO, United States and Carly Howett, Southwest Research Institute Boulder, Boulder, CO, United States
Abstract:
Estimates of the total power radiated by Enceladus' tiger stripes are constrained by Cassini CIRS observations of the thermal emission from the tiger stripe region. Unfortunately, these data have several limitations imposed by the nature of the CIRS instrument, and the very limited time available for high resolution observations of Enceladus' south pole. Short-wavelength (7 - 16 micron) maps have complete coverage with good spatial resolution, but do not capture the bulk of the radiated power, which is emitted at longer wavelengths. Long-wavelength (> 16 micron) maps which capture most of the emission have either very limited spatial coverage, or spatial resolution insufficient to separate the tiger stripes from background thermal emission. In Howett et al. (2011) we estimated ~16 GW of total endogenic heat flow based on low-resolution long-wavelength data. This estimate required model-dependent assumptions about passive background thermal emission, which was not directly separated spatially from the tiger stripes, but included potential inter-stripe endogenic background emission. Our recent much lower estimate of emission from the tiger stripes alone, ~4.5 GW (Spencer et al. 2013), uses high-resolution long-wavelength data to exclude both passive and possible endogenic inter-stripe emission, but is based on poorly-constrained extrapolations to the entire system of long-wavelength observations of small portions of the tiger stripes. We eagerly await the one remaining opportunity to extend long-wavelength, high spatial resolution, mapping to more of the tiger stripe system in Cassini's final close Enceladus flyby, in December 2015. In the meantime, existing long-wavelength data of intermediate spatial resolution provides intriguing additional clues about the true spatial distribution, and thus the total power, of the long-wavelength emission. In particular, a March 2008 scan of Damascus and Baghdad Sulci shows surprisingly bright 16 - 200 micron emission at the anti-Saturn end of these tiger stripes, which may indicate excess endogenic power, either from the tiger stripes or the inter-stripe regions, that is not included in our 2013 heat flow estimate.
