University of Toronto astronomer Evelyn Macdonald and her colleagues have identified substantial differences in surface temperature, sea ice and water vapor across an exoplanet’s surface for different land configurations.
Many exoplanets are tidally locked to their stars such that one side of the planet is always facing away.
This creates permanent day and night sides of the planet where the all energy received from the star is focused on the dayside.
In order for a planet to support life, the climate must be somewhat regulated across the surface: the atmosphere and oceans need to redistribute some of the energy received from the star to the nightside of the planet.
In the new research, Macdonald and co-authors developed a new 3D climate model, named ExoPlaSim, and used it to systematically vary dayside land cover on an Earth-like planet under two extreme and opposite continent configurations.
The first configuration is a circular continent in the middle of the dayside surrounded by ocean.
The second configuration is the opposite: a circular ocean in the middle of the dayside with land everywhere else.
For both cases, the size of the circle was varied to demonstrate how the planet’s climate depends on land fraction for each of these continent configurations.
Among other things, a planet’s habitability is dependent on its surface temperature and the amount of moisture in its atmosphere.
The authors modeled the net precipitation, cloud fraction, and surface temperature across the dayside of the planet for different land configurations.
Their results show that both the amount of land, and its configuration can have a large effect on the surface conditions of the planet.
For models with similar dayside land fractions but opposing configurations, the average surface temperature can change by up to 20 degrees Celsius.
The results indicate that the amount of water vapor in the planet’s atmosphere heavily depends on the area of ice-free ocean on its surface.
Planets with high land fractions have hotter and drier daysides with clouds and precipitation mostly confined to small central areas.
“Finding out whether life exists elsewhere in the Universe is a key challenge of astronomy and science as a whole,” Macdonald said.
“Our work demonstrates that the distribution of land on an Earth-like planet has a big impact on its climate, and should help astronomers looking at planets with instruments like the NASA/ESA/CSA James Webb Space Telescope to better interpret what they’re seeing.”
The results appear in two papers in the Monthly Notices of the Royal Astronomical Society.
Evelyn Macdonald et al. 2022. Climate uncertainties caused by unknown land distribution on habitable M-Earths. MNRAS 513 (2): 2761-2769; doi: 10.1093/mnras/stac1040
Adiv Paradise et al. 2022. ExoPlaSim: Extending the Planet Simulator for exoplanets. MNRAS 511 (3): 3272-3303; doi: 10.1093/mnras/stac172
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