Study: The location and amount of land on the planet’s surface can have a significant impact on its habitability

University of Toronto astronomer Evelyn Macdonald and her colleagues have identified substantial differences in surface temperature, sea ice, and water vapor at the surface of an exoplanet for different Earth configurations.

macdonalds et al. show that the amount of land and its configuration can have a large effect on the surface conditions of an exoplanet. Image credit:

Many exoplanets are tidally locked to their stars, so one side of the planet always faces outward.

This creates permanent day and night sides of the planet where all energy received from the star is focused on the day side.

For a planet to support life, the climate must be somewhat regulated on the surface: the atmosphere and the oceans must redistribute part of the energy received from the star towards the night side of the planet.

In the new research, Macdonald and his co-authors developed a new 3D climate model, named ExoPlaSim, and used it to systematically vary daytime land cover on an Earth-like planet under two extreme and opposite continental configurations.

The first configuration is a circular continent in the middle of the dayside surrounded by the ocean.

The second configuration is the opposite: a circular ocean in the middle of the dayside with land everywhere else.

In both cases, the size of the circle has been changed to demonstrate how the planet’s climate depends on the fraction of land for each of these continent configurations.

Among other things, the habitability of a planet depends on its surface temperature and the amount of moisture in its atmosphere.

The authors modeled net precipitation, cloud fraction, and surface temperature on the dayside of the planet for different land configurations.

Their results show that the amount of land and its configuration can have a large effect on the planet’s surface conditions.

For models with similar land fractions but opposite configurations, the average surface temperature can vary by up to 20 degrees Celsius.

The results indicate that the amount of water vapor in the planet’s atmosphere is highly dependent on the area of ​​the ocean without ice on its surface.

Planets with high terrestrial fractions have hotter, drier daytime sides with clouds and precipitation mostly confined to small central areas.

“Knowing whether life exists elsewhere in the Universe is a key challenge for astronomy and science as a whole,” Macdonald said.

“Our work demonstrates that the distribution of land on an Earth-like planet has a large impact on its climate and should help astronomers observing planets with instruments such as the NASA/ESA/CSA James Webb Space Telescope to better interpret what they are. seer.”

The results appear in two articles of the Royal Astronomical Society Monthly Notices.


Evelyn Macdonald et al. 2022. Climate Uncertainties Caused by Unknown Land Distribution on Habitable M-Earths. MNRAS 513 (2): 2761-2769; do I: 10.1093/mnras/stac1040

Paradise Adiv et al. 2022. ExoPlaSim: extension of the planet simulator for exoplanets. MNRAS 511(3):3272-3303; do I: 10.1093/mnras/stac172

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