Searching for new endogenic heat sources on Enceladus

The south polar region of Enceladus is a source of endogenic heat and plumes, as discovered using observations by Cassini instruments (e.g. Spencer et al. 2006). They comprise four long fissures or ‘Tiger Stripes’ which exude considerable thermal power; the total heat flow is likely between 4.2 GW (Spencer et al., 2018) and 15.8 ± 3.1 GW (Howett et al., 2011). The presence of further, smaller warm anomalous regions has not been ruled out, but would be important in understanding the heat budget and evolution of Enceladus' crust above the liquid ocean beneath.

We use observations from Cassini’s Composite Infrared Spectrometer (CIRS) to survey the non-south polar regions of Enceladus in an attempt to both identify other low-level endogenic heat sources and to assess the limits of the observations for the detection of such sources.

We compare CIRS temperatures to those from seasonal 1D surface thermal model to estimate expected temperature. We establish a time and latitude dependent model uncertainty based on predicted uncertainties in thermal inertia and albedo. These are used alongside estimated CIRS temperature errors in order to establish whether departures from expected temperatures are significant or reliable. We explore candidate observations and discuss their validity, as well as establishing the measurement limits that are required to be met in order to establish whether endogenic heat sources exist outside the south polar terrain of Enceladus.