Modeling Atmospheric Ion Escape from Kepler-1649 b and c over Time

Abstract

Rocky planets orbiting M-dwarf stars are prime targets for atmospheric characterization, yet their long-term evolution under intense stellar winds and high-energy radiation remains poorly constrained. The Kepler-1649 system, hosting two terrestrial exoplanets orbiting an M5V star, provides a valuable laboratory for studying atmospheric evolution in the extreme environments typical of M-dwarf 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 0.8 to 4.0 Gyr. The results reveal a clear decline in total ion escape rates with stellar age, as captured by a nonparametric LOWESS regression, with O${}^{+}$ comprising 98.3%-99.9% of the total loss. Escape rates at 4.0 Gyr are two to three orders of magnitude lower than during early epochs. At 0.8 Gyr, planet b exhibits 3.79$\times$ higher O${}^{+}$ escape rates than planet c, whereas by 4.0 Gyr its O${}^{+}$ escape rate becomes 39.5$\times$ lower. This reversal arises from a transition to sub-magnetosonic star-planet interactions, where the fast magnetosonic Mach number, $M_f$, falls below unity. Despite substantial early atmospheric erosion, both planets may have retained significant atmospheres, suggesting potential long-term habitability. These findings offer predictive insight into atmospheric retention in the Kepler-1649 system and inform future JWST observations of similar M-dwarf terrestrial exoplanets aimed at refining habitability assessments.

arXiv comment19 pages, 6 figures, 3 tables, published in The Astrophysical Journal Letters (ApJL)

References in corpus (67)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Modules for Experiments in Stellar Astrophysics (MESA)
• MESA Isochrones and Stellar Tracks (MIST) 0: Methods for the construction of stellar isochrones
• Exoplanet Biosignatures: A Review of Remotely Detectable Signs of Life
• New Mass Loss Measurements from Astrospheric Lyman-alpha Absorption
• The MUSCLES Treasury Survey I: Motivation and Overview
• Planetary Spectrum Generator: an accurate online radiative transfer suite for atmospheres, comets, small bodies and exoplanets
• The Habitability of Planets Orbiting M-dwarf Stars
• Atmospheric Escape and the Evolution of Close-in Exoplanets
• How to Characterize Habitable Worlds and Signs of Life
• Impact of Space Weather on Climate and Habitability of Terrestrial Type Exoplanets
• The Detectability and Characterization of the TRAPPIST-1 Exoplanet Atmospheres with JWST
• VULCAN: an Open-Source, Validated Chemical Kinetics Python Code for Exoplanetary Atmospheres
• Exoplanet Biosignatures: A Framework for Their Assessment
• Atmospheric escape from the TRAPPIST-1 planets and implications for habitability
• Is Proxima Centauri b habitable? -- A study of atmospheric loss
• Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star
• Outgassing of Ordinary Chondritic Material and Some of its Implications for the Chemistry of Asteroids, Planets, and Satellites
• Atmosphere-interior exchange on hot rocky exoplanets
• The Space Weather of Proxima Centauri b
• Habitability of Terrestrial-Mass Planets in the HZ of M Dwarfs. I. H/He-Dominated Atmospheres
• On the Frequency of Potential Venus Analogs from Kepler Data
• The effects of stellar winds on the magnetospheres and potential habitability of exoplanets
• Atmospheres of Rocky Exoplanets
• Atmospheric mass loss by stellar wind from planets around main sequence M stars
• The Upper Atmospheres of Terrestrial Planets: Carbon Dioxide Cooling and the Earth's Thermospheric Evolution
• The High-Energy Radiation Environment Around a 10 Gyr M Dwarf: Habitable at Last?
• Extreme hydrodynamic losses of Earth-like atmospheres in the habitable zones of very active stars
• Modeling Martian Atmospheric Losses over Time: Implications for Exoplanetary Climate Evolution and Habitability
• The full spectral radiative properties of Proxima Centauri
• Habitable Zones in the Universe
• Hydrodynamic escape of water vapor atmospheres near very active stars
• Evaluating Rotation Periods of M Dwarfs Across the Ages
• Telling twins apart: Exo-Earths and Venuses with transit spectroscopy
• Survival of Terrestrial N2-O2 Atmospheres in Violent XUV Environments through Efficient Atomic Line Radiative Cooling
• Electron Physics in 3D Two-Fluid Ten-Moment Modeling of Ganymede's Magnetosphere
• The young Sun's XUV-activity as a constraint for lower CO${}_2$-limits in the Earth's Archean atmosphere
• 3D modelling of the impact of stellar activity on tidally locked terrestrial exoplanets: atmospheric composition and habitability
• The Effects of Magnetic Fields on Observational Signatures of Atmospheric Escape in Exoplanets: Double Tail Structures
• Atmospheric Escape From TOI-700 d: Venus versus Earth Analogs
• The impact of intrinsic magnetic field on the absorption signatures of elements probing the upper atmosphere of HD209458b
• Airy worlds or barren rocks? On the survivability of secondary atmospheres around the TRAPPIST-1 planets
• Eccentricity evolution in hierarchical triple systems with eccentric outer binaries
• A roadmap for the atmospheric characterization of terrestrial exoplanets with JWST
• Role of planetary obliquity in regulating atmospheric escape: G-dwarf vs. M-dwarf Earth-like exoplanets
• Implications of atmospheric nondetections for Trappist-1 inner planets on atmospheric retention prospects for outer planets
• The Demographics of Terrestrial Planets in the Venus Zone
• Eccentricity Driven Climate Effects in the Kepler-1649 System
• Kepler-1649b: An Exo-Venus in the Solar Neighborhood
• A Habitable-Zone Earth-Sized Planet Rescued from False Positive Status
• The dependence of the stability of hierarchical triple systems on the orbital inclination
• Rossby numbers of fully and partially convective stars
• Improved equations for eccentricity generation in hierarchical triple systems
• Revisiting the space weather environment of Proxima Centauri b
• MHD simulations of the space weather in Proxima b: Habitability conditions and radio emission
• Hierarchical Bayesian Atmospheric Retrieval Modeling for Population Studies of Exoplanet Atmospheres: A Case Study on the Habitable Zone
• The Space Environment and Atmospheric Joule Heating of the Habitable Zone Exoplanet TOI700-d
• On Earth's habitability over the Sun's main-sequence history: joint influence of space weather and Earth's magnetic field evolution
• Observing atmospheric escape in sub-Jovian worlds with JWST
• Automated chemical reaction network generation and its application to exoplanet atmospheres
• Impact of M-dwarf Stellar Wind and Photoevaporation on the Atmospheric Evolution of Small Planets
• Role of Planetary Radius on Atmospheric Escape of Rocky Exoplanets
• A New Definition of Exoplanet Habitability: Introducing the Photosynthetic Habitable Zone
• The Solar Neighborhood LI: A Variability Survey of Nearby M Dwarfs with Planets from Months to Decades with TESS and the CTIO/SMARTS 0.9 m Telescope
• Exosphere Modeling of Proxima b: A Case Study of Photochemical Escape with a Venus-like Atmosphere
• Three-dimensional, Time-dependent MHD Simulation of Disk-Magnetosphere-Stellar Wind Interaction in a T Tauri, Protoplanetary System