Atmospheric Escape From TOI-700 d: Venus vs. Earth Analogs

Steady-state stellar wind characteristics of TOI-700. (a) The 3D stellar wind configuration comprising select magnetic field lines. Contours in the background illustrate stellar wind speed at the equatorial plane (z = 0). The blue isosurface signifies the critical surface beyond which the stellar wind becomes super-magnetosonic (or “superfast”). Black solid lines indicate the orbits of three planets, namely, TOI-700 b, TOI-700 c, and TOI-700 d. (b) Stellar wind dynamic pressure in the equatorial plane normalized by the solar wind dynamic pressure at 1 AU. (c) Stellar wind density in the equatorial plane normalized by the solar wind density at 1 AU. In panels (b) and (c), the dashed line represents the critical surface location.

The recent discovery of an Earth-sized planet (TOI-700 d) in the habitable zone of an early-type M-dwarf by the Transiting Exoplanet Survey Satellite constitutes an important advance.

In this Letter, we assess the feasibility of this planet to retain an atmosphere - one of the chief ingredients for surface habitability - over long timescales by employing state-of-the-art magnetohydrodynamic models to simulate the stellar wind and the associated rates of atmospheric ion escape. We take two major factors into consideration, namely, the planetary atmospheric composition and magnetic field.

In all cases, we determine that the atmospheric ion escape rates are potentially a few orders of magnitude higher than the inner Solar system planets, but TOI-700 d is nevertheless capable of retaining a 1-bar atmosphere over gigayear timescales for certain regions of the parameter space. We also discuss the prospects for detecting radio emission of the planet (thereby constraining its magnetic field) and discerning the presence of an atmosphere.

Chuanfei Dong, Meng Jin, Manasvi Lingam
Comments: 8 pages, 3 figures, and 1 table
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Space Physics (
Cite as: arXiv:2005.13190 [astro-ph.EP] (or arXiv:2005.13190v1 [astro-ph.EP] for this version)
Submission history
From: Chuanfei Dong
[v1] Wed, 27 May 2020 06:37:21 UTC (4,219 KB)

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