Profiles of temperature and ethane derived from models of VLT/VISIR 12.25 μm spectroscopy of the impact site. Two different techniques for fitting the data were attempted. In the upper panels we fit the data by varying T(p) (a)−b)) and the C₂H₆ abundances simultaneously (c)−e)). In the lower panels we fit the data by varying C₂H₆ alone (f)−h)). In all cases, the solid lines are results for July 26, the dashed lines are results for August 13. The dotted lines show the formal retrieval error on the vertical profiles, though these are omitted from panels a, c and f for clarity. An enhancement of ethane is required in both scenarios.