Fundamentals for habitable scenarios for Earth-like planets in the TRAPPIST-1 system

Abstract

The characterization of rocky exoplanets in the Habitable Zone (HZ) of their stars has entered a new era with the launch of the JWST. The TRAPPIST-1 star system is a particularly interesting target for observations, with its seven Earth-sized planets. An insightful body of work for a wide range of atmospheres has shown them to be intriguing candidates for analysis to learn more about terrestrial planets and their evolution. However, unknowns remain in analyses of changing conditions for planets with Earth-analogue atmospheres (N2-CO2-H2O) for the whole system, as well as what spectral features JWST could search for in such environments. Here, we explore the specific question of how rocky Earth-analogue planets could evolve at the position of the TRAPPIST-1 planets and assess the conditions that could lead to surface temperatures above freezing for the planets in the HZ. We found that three of the seven planets could provide warm surface conditions for Earth-analogue atmospheres. Our models show marked differences in the resulting transmission spectra. The first JWST observation of the atmosphere for TRAPPIST-1 planets have recently been published to exclude widely extended atmospheres without clouds, but more observations are needed to put constrains on models for terrestrial atmospheres.