Evolving Atmospheric Ion Escape from Kepler-1649 b and c: Power-Law Trends in Atmospheric Loss
Rocky planets orbiting M-dwarf stars are prime targets for characterizing terrestrial atmospheres, yet their long-term evolution under intense stellar winds and high-energy radiation remains poorly understood.
The Kepler-1649 system, which hosts two terrestrial exoplanets orbiting an M5V star, presents a valuable opportunity to explore atmospheric evolution in the extreme environments characteristic of M-dwarf stellar systems.
In this Letter we show that both planets could have retained atmospheres over gigayear timescales. Using a multi-species magnetohydrodynamic model, we simulate atmospheric ion escape driven by stellar winds and extreme ultraviolet radiation from 0.7 to 4.8 Gyrs. The results show that total ion escape rates follow a power-law decline (∝τ−1.6 for Kepler-1649 b, ∝τ−1.5 for Kepler-1649 c), with O+ dominating atmospheric loss (76.8%-98.7%).
The escape rates at 4.8 Gyrs are two orders of magnitude lower than those during the early epochs (1.9×1027 s−1 at 0.7 Gyr vs. 3.0×1025 s−1 at 4.8 Gyrs for planet b), while planet b consistently exhibits 1.1-1.9× higher O+ escape rates than planet c due to its closer orbit (0.051 AU vs. 0.088 AU).
Despite substantial early atmospheric erosion, both planets may still retain significant atmospheres, suggesting the potential for long-term habitability. These findings offer predictive insight into atmospheric retention in M-dwarf systems and inform future JWST observations aimed at refining habitability assessments.
Haitao Li, Xinke Wang, Chuanfei Dong, Lianghai Xie, Xinyi He, Hong-Liang Yan, Jinxiao Qin, Nathan Mayne, Mei Ting Mak, Nikolaos Georgakarakos, Duncan Christie, Yajun Zhu, Zhaojin Rong, Jinlian Ma, Shi Chen, Hai Zhou
Comments: 19 pages, 6 figures, 3 tables. Submitted to ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2504.12541 [astro-ph.EP] (or arXiv:2504.12541v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2504.12541
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Submission history
From: Haitao Li
[v1] Thu, 17 Apr 2025 00:07:53 UTC (6,259 KB)
https://arxiv.org/abs/2504.12541
Astrobiology,
