Atmosphere retention by terrestrial planets orbiting M dwarfs

Ascertain whether terrestrial planets orbiting M-dwarf stars can retain atmospheres to the present day, given the stars’ elevated activity levels and extended pre-main-sequence phases.

Background

M-dwarf stars have higher activity and longer pre-main-sequence lifetimes than Sun-like stars, leading to enhanced XUV irradiation that threatens atmospheric survival for close-in terrestrial planets.

Despite intensive observational efforts, detections of atmospheres around terrestrial M-dwarf planets have been largely negative or inconclusive, and the authors explicitly state that whether such planets can retain atmospheres to the present day remains unclear.

References

It is thus unclear whether, if they did originally form with an atmosphere, a terrestrial M dwarf planet can retain said atmosphere to the present day.

— New Constraints on the M Dwarf Cosmic Shoreline from a Galaxy Far, Far Away  (2603.29743 - Radica, 31 Mar 2026) in Section 1 (Introduction)

We note that we cannot rule out the possibility that the X-ray luminosities of our targets are lower than the range previously observed for M dwarfs, although investigating this possibility is beyond the scope of the present study.

— A Search for helium in the atmospheres of three sub-Neptunes and a super-Earth around M-dwarfs  (2608.19030 - Kawauchi et al., 19 Aug 2026) in Section 5.3, “Impact of X-ray Flux Uncertainty”

The question remains if secondary atmospheres can be formed and maintained on such planets \citep{krissansen-totton:2024}.

— Looking for TRAPPIST-1 external planets' emission in JWST archival data  (2608.18626 - Cartigny et al., 19 Aug 2026) in Section 1, Introduction