TRAPPIST-1e: High-Hope Exoplanet with 0.95 ESI Faces Tidal Lock Challenge

TRAPPIST-1e, boasting a 0.95 Earth Similarity Index (ESI), leads seven rocky planets in its system as the most likely to harbor life. But its closeness to the host star has tidally locked all planets, trapping one side in perpetual light and the other in darkness—leaving only a narrow twilight zone as a potential life haven.

June 27, 2025, 1:31 pm EDT· 1 minute read

Tidal locking forces TRAPPIST-1e to forever face one side toward its star, creating stark contrasts:

Day Side: Baked by constant radiation, temperatures may exceed 100°C, boiling surface water.
Night Side: Permanently frigid, with temperatures plunging below -100°C, freezing water solid.
Terminator Zone: A thin boundary between day and night could maintain 0–40°C, ideal for liquid water.
Models suggest a thick atmosphere might circulate heat, but the planet’s fate hinges on balancing stellar radiation with atmospheric resilience.

Despite challenges, TRAPPIST-1e remains a prime target:

Atmospheric Biomarkers: The James Webb Space Telescope will analyze its transit spectra for signs of methane or ozone.
Subsurface Potential: Tidal heating from neighboring planets could sustain underground oceans, shielding life from surface extremes.
Redefining Habitability: The case shows habitability may lie in twilight zones, not just perfect Earth clones.
As astronomers probe this cosmic paradox, TRAPPIST-1e underscores that life’s resilience may thrive where day and night meet, challenging notions of where to seek extraterrestrial worlds.