TRAPPIST-1 d: Exo-Venus, Exo-Earth or Exo-Dead?

TL;DR

This study uses 3D climate modeling to explore whether TRAPPIST-1 d could be habitable, an exo-Venus, or an exo-Dead world, depending on its atmospheric conditions and parameters.

Contribution

It demonstrates that TRAPPIST-1 d could be habitable or a Venus-like or dead planet within a narrow parameter space using advanced climate simulations.

Findings

TRAPPIST-1 d may reside within the habitable zone under certain conditions.

The planet could also be an exo-Venus or exo-Dead depending on atmospheric parameters.

Modeling helps distinguish between different planetary types in the TRAPPIST-1 system.

Abstract

TRAPPIST-1 d is generally assumed to be at the boundary between a Venus-like world and an Earth-like world, although recently published works on TRAPPIST-1 b and c raise concerns that TRAPPIST-1 d may be similarly devoid of a substantial atmosphere. TRAPPIST-1 d is also relatively understudied in comparison with TRAPPIST-1 e. The latter has generally appeared to be within the habitable zone of most atmospheric modeling studies. Assuming that TRAPPIST-1 d still retains a substantial atmosphere, we demonstrate via a series of 3D general circulation model experiments using a dynamic ocean that the planet could reside within the habitable zone in a narrow parameter space. At the same time, it could also be an exo-Venus or exo-Dead-type world or in transition between between one of these. Studies like this can help distinguish between these types of worlds.