Upper Atmosphere Dynamics And Drivers Of Volatiles Loss From Terrestrial-type (exo)Planets

Volatile loss from exoplanetary atmospheres and its possible implications for the longevity of habitable surface conditions is a topic of vigorous debate currently.

The vast majority of the habitable zone terrestrial-like exoplanets known to date orbit low-mass M- and K-dwarf stars and are subject to the conditions drastically different to those of terrestrial planets in the Solar System.

In particular, they orbit far closer to their host stars than similar planets around G-dwarfs similar to the Sun. Therefore they receive higher X-ray and UV fluxes, even though luminosities of M- and K-dwarfs are lower than those of heavier stars. Furthermore, due to their slower evolution, M-dwarfs retain high activity on the gigayear timescales.

The combination of these two effects has led to claims that most terrestrial planets orbiting M-dwarfs may have their atmospheres stripped from the higher X-ray and UV fluxes of their host stars. Opposing this are researchers who point out that volatile inventories for terrestrial exoplanets are ill-constrained, and hence, they may be able to “weather the storm” of these higher X-ray and UV fluxes.

In this chapter, we focus on exploring volatile loss in the upper atmospheres of terrestrial planets in our solar system and applications to those in exoplanetary systems around stars of different types.

Schematic illustrations of (a) ion escape routes from a magnetized planet (modified from Seki et al, 2001) and (b) atmospheric escape mechanisms from unmagnetized planets. In panel (a), ○a and ○b show outflow and return flow from/to the ionosphere, respectively. The escape routes ○ii , ○iii , and ○iv in the panel (a) result from polar wind and auroral outflows, while routes ○i and ○v correspond to the plasmaspheric drainage plume and ENA production by charge exchange between the ring current ions and geocorona. — astro-ph.EP

Daria Kubyshkina, Michael J. Way, Iannis Dandouras, Helmut Lammer, Antonino Francesco Lanza, Manasvi Lingam, Rumi Nakamura, Moa Persson, Manuel Scherf, Kanako Seki

Comments: 100 pages, 22 figures, 3 tables. Accepted for publication in Space Science Reviews (Topical collection “Geoscience of Exoplanets”)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2602.15507 [astro-ph.EP] (or arXiv:2602.15507v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2602.15507
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Submission history
From: Daria Kubyshkina
[v1] Tue, 17 Feb 2026 11:29:29 UTC (8,639 KB)
https://arxiv.org/abs/2602.15507

Astrobiology, exoplanet,