A transmission spectrum of WASP-39 b. The circles with error bars show the JWST NIRSpec PRISM spectrum in the 3–5 μm range reduced with the Tiberius pipeline (The JWST Transiting Exoplanet Community Early Release Science Team et al. 2022) along with prior HST/WFC3 observations in the 0.8–1.7 μm range (Wakeford et al. 2018). The solid curve in brown shows our retrieved best-fit spectrum, and the same spectrum but without opacity contributions from aerosols is shown in blue for reference (see Section 4.2.1). The heights of the prominent spectral features in the JWST and HST bands in terms of a characteristic atmospheric scale height are denoted by arrows; a nominal slant photospheric temperature of 800 K is assumed motivated by the retrieved constraints. The contributions of individual molecules are shown in Figure 6 in the Appendix.