Extended Data Fig. 2: MIRI spectroscopic modeling inputs for the CH3 analysis.
From: The atmosphere of Titan in late northern summer from JWST and Keck observations
(a) Nominal and end-member temperature profiles and CH3 profile. Stratospheric and mesospheric temperatures are based on Cassini CIRS temperature inversions from 2008.8 (half a Titan year earlier for seasonal correspondence in the latitude range ± 45∘N). Thermospheric temperatures are highly variable and end-member profiles are based on low latitude results from Cassini UVIS and INMS, the Huygens probe entry profile at 15∘S, and ALMA equatorial observations. b) non-LTE emission ratio for the range of k1 values and temperatures considered. The grey region shows the uncertainty in the non-LTE effect and the vertical dotted line shows the LTE case for comparison. (c–f) Normalised contribution functions (dR/dx where R is radiance and x is log(VMR) for the LTE and non-LTE cases). The non-LTE effect suppresses the thermospheric emission peak so most emission is from the stratopause region in the nominal temperature and k1=7 × 10−13 cm3 s−1 case. Note the slightly negative contribution functions in the thermosphere originate from weak CH3 absorption due to the high abundance, combined with negligible non-LTE emission at those altitudes.
