2017/03/16 by Eric T. Wolf, Eric Wolf · 1 voice · 5 citations
Earth and Planetary Sciences · Environmental Science · Physics and Astronomy · #Atmospheric Ozone and Climate #Climate variability and models #Stellar, planetary, and galactic studies #astro-ph.EP
paper · pdf · doi:10.3847/2041-8213/aa693a
Submitted to ApJL, 5 figures, New version includes errata appended to the end
arxiv published 2017/03/16 · openalex publication_date 2017/04/06 · openalex created_date 2017/04/14 · arxiv created 2018/03/31 · arxiv updated 2018/04/03 · openalex updated_date 2026/07/28
The TRAPPIST-1 system provides an extraordinary opportunity to study multiple terrestrial extrasolar planets and their atmospheres. Here we use the National Center for Atmospheric Research Community Atmosphere Model version 4 to study the possible climate and habitability of the planets in the TRAPPIST-1 system. We assume ocean-covered worlds, with atmospheres comprised of N2, CO2, and H2O, and with orbital and geophysical properties defined from observation. Model results indicate that the inner three planets (b, c, and d) presently reside interior to the inner edge of the traditional liquid water habitable zone. Thus if water ever existed on the inner planets, they would have undergone a runaway greenhouse and lost their water to space, leaving them dry today. Conversely the outer 3 planets (f, g, and h) fall beyond the maximum CO2 greenhouse outer edge of the habitable zone. Model results indicate that the outer planets cannot be warmed despite as much as 30 bar CO2 atmospheres, instead entering a snowball state. The middle planet (e) represents the best chance for a presently habitable ocean-covered world in the TRAPPIST-1 system. Planet e can maintain at least some habitable surface area with 0 - 2 bar CO2, depending on the background N2 content. Near present day Earth surface temperatures can be maintained for an ocean-covered planet e with either 1 bar N2 and 0.4 bar CO2, or a 1.3 bar pure CO2 atmosphere.