New climate models have shown that the amount and location of land on a planet’s surface can significantly affect its habitability. Astronomers have identified significant differences in surface temperature, sea ice and water vapor on the planet’s surface in various land configurations.
Many planets are tidally locked to their stars in such a way that one side of the planet always faces away (much like the dark side of the Moon always faces away from Earth). This creates a permanent day and night side of the planet, where all the energy received from the star is concentrated on the day side. In order for life to exist on the planet, the climate must be regulated to a certain extent over the entire surface: the atmosphere and oceans must redistribute some of the energy received from the star to the night side of the planet.
A team of researchers from the University of Toronto used a 3D climate model (ExoPlaSim) to construct Earth-like planets with two different dayside configurations. The first configuration is a circular continent in the center of the day side, surrounded by an ocean. The second configuration is the opposite, with a circular ocean at the center of the day side and land everywhere. In both cases, the size of the circle was varied to show how the planet’s climate depends on the proportion of land for each of these configurations of continents.
Among other things, the habitability of a planet depends on the temperature of its surface and the amount of moisture in the atmosphere. The study models net precipitation, cloud fraction and surface temperature on the planet’s dayside for various land configurations.
The results show that both the amount of land and its configuration can have a big impact on conditions on the planet’s surface. For models with the same proportion of land on the dayside but opposite configuration, the average surface temperature can change by ~20°C. The results show that the amount of water vapor in the planet’s atmosphere is highly dependent on the area of non-freezing ocean on its surface. Planets with a high proportion of land have hotter, drier days, and clouds and precipitation are mostly limited to small central regions.
Finding out whether life exists elsewhere in the universe is a key task for astronomy and science in general. Our work demonstrates that land distribution on an Earth-like planet has a major impact on its climate, and should help astronomers studying planets with instruments such as the James Webb Space Telescope to better interpret what they see.