Comparison between the transmission spectrum of TOI-270 d and K2-18 b observed with JWST/NIRSpec G395H. The spectra are binned to R ≈ 55 for visual clarity and are shown in orange and dark red, respectively. The K2-18 b spectrum is vertically offset by -41 ppm as discussed in Madhusudhan et al. (2023b). The two spectra show similar spectral features, coming predominantly from the absorption due to CH₄ and CO₂. The blue curves shows the median retrieved model spectrum obtained with the K2-18 b data from Madhusudhan et al. (2023b).