Characterizing atmospheres of cloudy temperate mini-neptunes with JWST

ABSTRACT The upcoming James Webb Space Telescope (JWST) promises a generational shift in the study of temperate mini-Neptune atmospheres using transit spectroscopy. High-altitude clouds, however, threaten to impede their atmospheric characterization by muting spectral features. In this study, we systematically investigate JWST instrument configurations for characterizing cloudy atmospheres, assessing importance choice and wavelength coverage, focusing on NIRISS NIRSpec. We consider two mini-Neptunes orbiting nearby M dwarfs, K2-18 b, TOI-732 c, with equilibrium temperatures below 400 K, as case studies assess observations different one per instrument. find that transmission spectra modest observing time adequate coverage can provide precise abundance constraints key molecules H2O, CH4, NH3 even presence clouds at significantly high altitudes. best are obtained combining all three high-resolution NIRSpec gratings (G140H+G235H+G395H) together span ?1–5 $\mu$m range. Single-transit three-instrument configuration allow cloud-top pressures low 3 0.1 mbar b respectively, assuming nominal 10× solar metallicity. vary combinations. G235H+G395H is optimal two-instrument configuration, while or G235H single-instrument observations. Absent high-altitude good these planets. Our findings underscore promise spectroscopy dwarfs.