Higher water loss on Earth-like exoplanets in eccentric orbits

Liu, Binghan; Marsh, D. R.; Walsh, Catherine; Cooke, Gregory

doi:10.1093/mnras/stad1828

Cited by 5 publications

(1 citation statement)

References 61 publications

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“…However, Figure A2 shows that during periods of high eccentricity, there are periods of time at aphelion where the limit is surpassed for Case 4. The latter is in line with recently published work by Liu et al (2023).…”

Section: Surface and Upper-atmosphere Specific Humiditysupporting

confidence: 93%

Exploring Climate with Obliquity in a Variable-eccentricity Earth-like World

Way,

Georgakarakos,

Clune

2023

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Exploring planetary systems similar to our solar system can provide a means to explore a large range of possibly temperate climates on Earth-like worlds. Rather than run hundreds of simulations with different eccentricities at fixed obliquities, our variable-eccentricity approach provides a means to cover an incredibly large parameter space. Herein Jupiter’s orbital radius is moved substantially inward in two different scenarios, causing a forcing on Earth’s eccentricity. In one case, the eccentricity of Earth varies from 0 to 0.27 over ∼7000 yr for three different fixed obliquities (0°, 23°, and 45°). In another case, the eccentricity varies from 0 to 0.53 over ∼9400 yr in a single case with zero obliquity. In all cases, we find that the climate remains stable, but regional habitability changes through time in unique ways. At the same time, the moist greenhouse state is approached but only when at the highest eccentricities.

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Section: Surface and Upper-atmosphere Specific Humiditysupporting

confidence: 93%

Exploring Climate with Obliquity in a Variable-eccentricity Earth-like World

Way,

Georgakarakos,

Clune

2023

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Stratospheric dayside-to-nightside circulation drives the 3D ozone distribution on synchronously rotating rocky exoplanets

Braam,

Palmer,

Decin

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Determining the habitability and interpreting future atmospheric observations of exoplanets requires understanding the atmospheric dynamics and chemistry from a 3-D perspective. Previous studies have shown significant spatial variability in the ozone layer of synchronously rotating M-dwarf planets, assuming an Earth-like initial atmospheric composition. We simulate Proxima Centauri b in an 11.2-day orbit around its M-type host star using a 3-D Coupled Climate-Chemistry model to understand the spatial variability of ozone and identify the mechanism responsible for it. We document a previously unreported connection between the ozone production regions on the photochemically active dayside hemisphere and the nightside devoid of stellar radiation and thus photochemistry. We find that stratospheric dayside-to-nightside overturning circulation can advect ozone-rich air to the nightside. On the nightside, ozone-rich air subsides at the locations of two quasi-stationary Rossby gyres, resulting in an exchange between the stratosphere and troposphere and the accumulation of ozone at the gyre locations. The mechanism drives the ozone distribution for both the present atmospheric level (PAL) and a 0.01 PAL O2 atmosphere. We identify the hemispheric contrast in radiative heating and cooling as the main driver of the stratospheric dayside-to-nightside circulation. An age-of-air experiment shows that the mechanism also impacts other tracer species in the atmosphere (gaseous and non-gaseous phase) as long as chemical lifetimes exceed dynamical lifetimes. These findings, applicable to exoplanets in similar orbital configurations, illustrate the 3-D nature of planetary atmospheres and the spatial and temporal variability that we can expect to impact spectroscopic observations of exoplanet atmospheres.

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Eccentric orbits may enhance the habitability of Earth-like exoplanets

Liu,

Marsh,

Walsh

et al. 2024

Monthly Notices of the Royal Astronomical Society

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The detection and characterization of Earth-like planets around Sun-like stars is an important goal of exoplanetary research, given their promise for hosting potentially habitable conditions. Key orbital parameters, such as eccentricity, can influence a planet’s climate response and, as a consequence, affect its potential habitability. Utilizing the Earth System Model - the Whole Atmosphere Community Climate Model (WACCM6), we simulated Earth-like exoplanets with two different orbital parameters: one circular (e = 0) and another highly eccentric (e = 0.4), both with zero obliquity but fixing the annual mean insolation. The highly eccentric case exhibits a 1.9 K warmer surface temperature due to lower surface and cloud albedo and a weaker longwave cloud forcing. Exploring the annual global mean climate difference, we analyzed latitudinal and seasonal variations in hydrological cycle variables, such as sea ice, land snow, and clouds. Land habitability metrics based on temperature and precipitation reveal that the e = 0.4 case has over 25% more habitable land area for more than 80% of its orbit, compared with the e = 0 case. Additionally, the global circulation pattern shifts from a three-cell to a two-cell system in the e = 0.4 case, expanding the Hadley cell to higher latitudes, enhancing meridional latent heat transport, and improving land habitability at higher latitudes. Our study suggests that Earth-like exoplanets with high eccentricity orbiting Sun-like stars may have greater land habitability than their circular counterparts, due to seasonally warmer surface temperatures and more evenly distributed precipitation over land.

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Higher water loss on Earth-like exoplanets in eccentric orbits

Cited by 5 publications

References 61 publications

Exploring Climate with Obliquity in a Variable-eccentricity Earth-like World

Exploring Climate with Obliquity in a Variable-eccentricity Earth-like World

Stratospheric dayside-to-nightside circulation drives the 3D ozone distribution on synchronously rotating rocky exoplanets

Eccentric orbits may enhance the habitability of Earth-like exoplanets

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