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The habitability of a planet is affected by the location of its land

A new study led by the University of Toronto has found that the amount and location of land on a planet’s surface can have a significant impact on its habitability. By applying three-dimensional climate models to simulated Earth-like planets, the experts have identified substantial differences in surface temperature, sea-ice, and water vapor across these planets’ surfaces for different types of land configurations.

Many planets are tidally locked to their stars so that one side of the planet is always facing away – just like the “dark side of the Moon” always faces away from the Earth. This phenomenon creates permanent day- and nightsides on such planets, with all the energy received from the star directed towards the planets’ daysides. However, in order for a planet to support life, the climate must be at least to a certain extent regulated across its surface. Thus, the planet’s atmosphere and oceans need to redistribute part of the energy received from the star to the planet’s nightside.

The scientists have applied a three-dimensional climate model (ExoPlaSim) to simulated Earth-like planets with two different dayside configurations: a circular continent in the middle of the dayside surrounded by ocean, and a circular ocean in the middle of the dayside surrounded by land everywhere else. In both cases, the size of the circle was varied in order to assess how the planet’s climate depends on the amount of land for each of the two configurations.

The results suggest that the amount of land, as well as its configuration have major effects on the surface conditions of the planet. For instance, for models with similar dayside land fractions but opposed configurations, the average surface temperature can change by up to 20 degrees Celsius. Thus, the amount of water vapor in a planet’s atmosphere – which is crucial for the planet’s habitability – strongly depends on the area of ice-free ocean on its surface. Moreover, planets with large patches of land 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,” said study lead author Evelyn Macdonald, a graduate student in Planetary Physics at the University of Toronto. 

“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 James Webb Space Telescope to better interpret what they’re seeing,” she concluded.

The study was presented on Monday, July 11 at the National Astronomy Meeting (NAM22) in Warwick. 

By Andrei Ionescu, Staff Writer  

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