Retention Of Surface Water On Tidally Locked Rocky Planets In The Venus Zone Around M Dwarfs
Terrestrial planets within the Venus zone surrounding M dwarf stars can retain surface ice caps on the perpetual dark side if atmospheric heat transport is inefficient, (as suggested by previous global climate simulations leconte2013) This condition is proposed to play a role in the potential regional habitability of these planets.
However, the amount of surface ice may be limited by considering the water condensed from the steam atmosphere in a runaway greenhouse state, and the physical mechanism for triggering the condensation process is not clear.
Here, we use a two-column moist radiative-convective-subsiding model to investigate the water condensation process on tidally locked planets from the runaway greenhouse state. We find that the water condensation process is characterized by two distinct equilibrium states under the same {(incoming stellar flux).
The initiation of condensation corresponds to a warm, unstable state exhibiting positive Planck feedback, whereas the termination phase corresponds to a cold, stable state exhibiting negative Planck feedback.
We further show that the surface water mass in the collapsed state (decreases with the) incoming stellar flux, background surface pressure, and optical thickness of non-condensible greenhouse gases, with a global equivalent depth of less than ∼20 cm. Our two-column approach provides a straightforward way to understand the water evolution on Venus zone planets around M dwarfs.
Schematic diagram illustrating a possible climate evolution of tidally locked planets in the Venus zone. Stage 1: primordial steam-dominated atmosphere is gradually lost by intense stellar radiation and atmospheric heat transport is weakened. Stage 2: water began to condense from the atmosphere to the surface. Stage 3: the planet is trapped in the collapsed state. Red and blue curves in panel(A) represent the evolution of surface temperature on the dayside and nightside, respectively. Orange and purple curves in panel(B) represent the evolution of atmospheric and surface water mass, respectively. — astro-ph.EP
Yueyun Ouyang, Feng Ding, Jun Yang
Comments: 19 pages, 3 figures, 1 table, accepted for publication in ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2505.13066 [astro-ph.EP] (or arXiv:2505.13066v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.13066
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Submission history
From: Yueyun Ouyang
[v1] Mon, 19 May 2025 12:57:20 UTC (231 KB)
https://arxiv.org/abs/2505.13066
Astrobiology,
