Posterior distributions (pdf) as derived from PASTA (blue histograms), with the violet area that highlights the 68.3% highest probability density interval. Left panel: rotation period pdf of TOI-2141 when the star was 150 Myr old (P_rot,150) compared with the P_rot,150 distribution of stars of comparable masses (black histogram) as extracted from the sample by Johnstone et al. (2015a). Right panel: initial atmospheric mass fraction ($f_{\text{atm}}^{\text{start}}$) pdf of TOI-2141 b compared with the model-inferred present-day atmospheric content (black line). The orange horizontal line marks the uniform prior that was imposed on $f_{\text{atm}}^{\text{start}}$.