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Determine the presence and properties of clouds and hazes in rocky exoplanet atmospheres

Characterize the presence, altitude, and optical properties of clouds and hazes in the atmospheres of rocky exoplanets, and quantify their impact on spectral observables and atmospheric interpretation.

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Background

Clouds and hazes can flatten or mute transmission spectra, confounding efforts to diagnose atmospheric composition and even the existence of an atmosphere. The working group underscores the uncertainty in the cloud/haze properties of rocky worlds and notes that stellar contamination further complicates interpretation of transmission data.

Understanding aerosol properties is necessary to design effective observation strategies and to interpret spectra obtained across wavelengths, including with JWST and supporting HST UV data.

References

Clouds and hazes are an additional unknown, though extrapolating from the Solar System and gaseous exoplanets, their presence would not come as a surprise.

— Report of the Working Group on Strategic Exoplanet Initiatives with HST and JWST (2404.02932 - Redfield et al., 2 Apr 2024) in Section 7, Frequently Asked Questions: Why not transits?