The temperature and width of an active fissure on Enceladus measured with Cassini VIMS during the 14 April 2012 South Pole flyover

The width and temperature of the active fissures on Saturn's satellite Enceladus provide key observable constraints on physical models of these geyser-like eruptions. We analyze a sequence of high spatial resolution near-infrared spectra acquired with VIMS at 0.025s intervals during a 74km altitude flyover of the South Pole of Enceladus by the Cassini spacecraft on 14 April 2012 UTC. A thermal-emission spectrum covering 3- to 5-μm wavelengths was detected as the field of view crossed one of the four major fissures, Baghdad Sulcus, within 1km of 82.36S latitude and 28.24W longitude. We interpret this spectrum as thermal emission from a linear fissure with temperature 197±20K and width 9m. At the above wavelengths, the spectrum is dominated by the warmest temperature component. Looking downward into the fissure at only 13° from the vertical, we conclude that our results measure the temperature of the interior fissure walls (and the H₂O vapor) at depths within 40m of the surface.