JWST Phase Curves Reveal Silicate Clouds Sustaining Reflective Atmosphere on Lava World TOI-561b
TOI-561b hosts a reflective atmosphere maintained by silicate clouds and interior volatile exchange, as shown by JWST phase-curve mapping. The result tightens constraints on atmospheric retention for the hottest rocky worlds and highlights the diagnostic power of full-orbit spectroscopy over eclipse-only data. Future longer-wavelength observations can test specific cloud compositions.
The 37-hour continuous NIRSpec observations explicitly model stellar granulation alongside the planetary phase curve and eclipse, producing a dayside emission spectrum robust to stellar variability. Energy balance arguments and general circulation model comparisons indicate the data require both high reflectivity and limited day-to-night heat transport, inconsistent with a bare-rock surface. Cloud formation maps from the GCMs place plausible SiO2 and MgSiO3 condensates on the dayside near the terminator, providing the observed albedo while permitting volatile replenishment from the interior. Prior density and eclipse-only measurements had already hinted at an atmosphere; the full-orbit dataset now confirms its global extent and cloud-driven reflectivity, overturning the expectation that intense stellar irradiation fully strips USP rocky planets of envelopes.
Dang et al.: MIRI 5-12 micron phase curves will detect SiO2 cloud absorption features at >3 sigma within 18 months if the reflective layer is silicate-dominated.
Sources (2)
- [1]Primary Source(https://arxiv.org/abs/2608.21519)
- [2]Supporting Source(https://arxiv.org/abs/2305.07755)