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Confirm heat redistribution efficiency on TRAPPIST-1 c

Determine whether TRAPPIST-1 c exhibits fully inefficient heat redistribution (consistent with an airless surface) or non-zero day–night heat transport indicative of an atmosphere by constraining its nightside flux and phase-curve offset from JWST/MIRI F1500W observations and complementary datasets.

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Background

Multiple independent reductions and global analyses were performed using JWST/MIRI data to derive phase curves for TRAPPIST-1 b and c. While TRAPPIST-1 b shows characteristics consistent with an airless body (large day–night contrast, no phase offset), the results for TRAPPIST-1 c are less definitive due to lower signal-to-noise and broader posteriors for nightside flux and phase offset.

The ED analysis explicitly notes that current data do not allow a definitive conclusion about heat redistribution on TRAPPIST-1 c, motivating further observational and modeling work to resolve whether the planet behaves as airless or retains a tenuous atmosphere with limited heat transport.

References

For TRAPPIST-1 c we measured a larger day-side temperature than night-side, however considering the still low SNR on the later it is not possible to confirm whether the heat redistribution is fully inefficient or not on this planet.

— First JWST thermal phase curves of temperate terrestrial exoplanets reveal no thick atmosphere around TRAPPIST-1 b and c (2509.02128 - Gillon et al., 2 Sep 2025) in Methods, Data reduction and analysis (ED), Results from the three global analyses