Atmospheric lifetime for a hypothetical Mars-sized planet orbiting Barnard’s Star

Dave A. Brain (1) , William K. Peterson (1) , Ofer Cohen (2) , Thomas Cravens (3) , Alison Farrish (4) , Kevin France (1) , Yoshifumi Futaana (5) , Katherine Garcia-Sage (4) , Alex Glocer (4) , Oliver Q. Hamil (3) , Mats Holmström (5) , Lynn M. Kistler (6) , François Leblanc (7) , Aimee W. Merkel (1) , Akifumi Nakayama (8) , Laura M. Peticolas (9) , Robin Ramstad (1) , Antonio Robin Renzaglia (3) , Shotaro Sakai (10) , Ryoya Sakata (8) , Neesha R. Schnepf (1) , Kanako Seki (8) , Robert J. Strangeway (11) , Wenyi Sun (12) , Naoki Terada (13) , Aline Vidotto (14)

1 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
2 CfA - Harvard-Smithsonian Center for Astrophysics
3 University of Kansas [Kansas City]
4 GSFC - NASA Goddard Space Flight Center
5 IRF - Swedish Institute of Space Physics [Kiruna]
6 UNH - University of New Hampshire
7 HELIOS - LATMOS
8 UTokyo - The University of Tokyo
9 UC Berkeley - University of California [Berkeley]
10 Hokkaido University [Sapporo, Japan]
11 UC - University of California
12 UCLA - University of California [Los Angeles]
13 Tohoku University [Sendai]
14 Universiteit Leiden = Leiden University

Atmospheric escape from exoplanets is a topic of great interest for the exoplanet community since atmospheric retention is an important component of surface habitability. While atmospheric escape has been detected from large exoplanets, it remains difficult to measure for smaller (rocky) planets. Indeed, for rocky planets orbiting active stars it is thought that it may be difficult for atmospheres to be retained at all. In the absence of detailed observations, one option is to leverage observations and models for planets in our own solar system. Here we consider atmospheric escape from Mars – if it orbited an M Dwarf star similar to Barnard’s star. Our analysis considers five escape processes: hydrodynamic escape, thermal escape, photochemical escape, ion escape, and sputtering. To estimate the escape rate via each process from our hypothetical “ExoMars”, we employ models for escape that have either been validated using observations or verified against other models. We provide escape rate estimates for important species in the Martian upper atmosphere: O, O2, H, and CO2, and use them to estimate the lifetime of the Martian atmosphere.

Domaines: Planète et Univers [physics]

Dave A. Brain, William K. Peterson, Ofer Cohen, Thomas Cravens, Alison Farrish, et al.. Atmospheric lifetime for a hypothetical Mars-sized planet orbiting Barnard’s Star. AGU Fall Meeting 2022, Dec 2022, Chicago, United States. pp.P42E-2450. ⟨insu-03922183⟩