The habitability of Proxima Centauri b II. Possible climates and Observability

By M. Turbet, J. Leconte, F. Selsis, É. Bolmont, Francois Forget, I. Ribas, S. Raymond, G. Anglada-Escud'e. 2016

223 citations recorded by the source corpus.

Radial velocity monitoring has found the signature of a $M \sin i = 1.3$~M$_\oplus$ planet located within the Habitable Zone (HZ) of Proxima Centauri \citep{Anglada16}. Despite a hotter past and an active host star the planet Proxima~b could have retained enough volatiles to sustain surface habitability \citep{Ribas2016}. Here we use a 3D Global Climate Model (GCM) to simulate Proxima b's atmosphere and water cycle for its two likely rotation modes (1:1 and 3:2 spin-orbit resonances) while varying the unconstrained surface water inventory and atmospheric greenhouse effect. We find that a broad range of atmospheric compositions allow surface liquid water. On a tidally-locked planet with sufficient surface water inventory, liquid water is always present, at least in the substellar region. With a non-synchronous rotation, this requires a minimum greenhouse warming ($\sim$10~mbar of CO$_2$ and 1~bar of N$_2$). If the planet is dryer, $\sim$0.5~bar/1.5~bars of CO$_2$ (respectively for asynchronous/synchronous rotation) suffice to prevent the trapping of any arbitrary small water inventory into polar/nightside ice caps. We produce reflection/emission spectra and phase curves for the simulated climates. We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes. The angular separation of $7 \lambda/D$ at 1~$\mu$m (with the E-ELT) and a contrast of $\sim$10$^{-7}$ will enable high-resolution spectroscopy and the search for molecular signatures, including H$_2$O, O$_2$, and CO$_2$. The observation of thermal phase curves can be attempted with JWST, thanks to a contrast of $2\times10^{-5}$ at 10~$\mu$m. Proxima~b will also be an exceptional target for future IR interferometers. Within a decade it will be possible to image Proxima~b and possibly determine whether this exoplanet's surface is habitable.

Subfields: Astronomy and Astrophysics, Instrumentation

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. L. Kaltenegger
2. Nuno C. Santos
3. E. Wolf
4. S. Udry
5. A. Reiners
6. D. Charbonneau
7. X. Delfosse
8. F. Selsis

In Instrumentation

1. Nuno C. Santos
2. S. Udry
3. A. Reiners
4. L. Kaltenegger
5. C. Lovis
6. F. Pepe
7. J. Morin
8. V. Meadows

Citations in the corpus

• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present (2016, background): “Here – as well as in a companion paper (Turbet et al. 2016, hereafter Paper II) – we address a number of factors related to the potential habitability of Proxima b. Defining planet habitability is not straightforward.”
• Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model (2017, background): “Gillon et al. (2017) assert that 3D climate model simulations of terrestrial planets around low-mass stars (e.g., Turbet et al. 2016) indicate that planets b, c, and d would undergo a runaway greenhouse, while planets e, f, and g could be habitable given “Earth-like” atmospheres.”
• Is Proxima Centauri b Habitable? A Study of Atmospheric Loss (2017, background): “In reality, we wish to note there are many possibilities for the atmospheric composition of PCb, provided that it even exists (Ribas et al. 2016; Turbet et al. 2016; Goldblatt 2016).”
• Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets (2017, background): “The reader is refered to Turbet et al. 2016 (in particular, their Figure 1) for a detailed discussion on the possible climate regimes on TRAPPIST-1e, analogous to Proxima Cen b.”
• Atmospheric characterization of Proxima b by coupling the Sphere high-contrast imager to the Espresso spectrograph (2016, background): “The question of a habitable climate on Proxima b is a complex one that is being addressed by numerous studies (e.g. Ribas et al. 2016; Turbet et al. 2016; Meadows et al. 2016).”
• Evolved Climates and Observational Discriminants for the TRAPPIST-1 Planetary System (2018, background): “More recently, comprehensive studies of Proxima Centauri b were undertaken by Turbet et al. (2016) using 3D general circulation models (GCMs) and by Meadows et al. (2018a) using 1D coupled climate–photochemical models.”
• Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs (2017, background): “…et al. 2007; Wordsworth et al. 2010; Abe et al. 2011; Haqq-Misra & Kopparapu 2015; Barnes et al. 2016; Meadows et al. 2016; Ribas et al. 2016; Turbet et al. 2016; Bolmont et al. 2017), and studies such as these provide a valuable contribution in understanding, and eventually interpreting,…”
• How to Characterize Habitable Worlds and Signs of Life (2017, background): “Without further observational constraints, a variety of atmospheres are possible for Proxima b (e.g., Meadows et al. 2016, Ribas et al. 2016, Turbet et al. 2016).”