Exoplanet study reveals uniqueness of Earth’s climate

Studies conducted on terrestrial exoplanets have shown that Earth’s land-water balance is highly unusual and unique to our planet.

Researchers at the International Space Science Institute studied how the evolution of continents and water shaped the evolution of exoplanets that exist outside our solar system. The discovery was presented at the Europlanet Science Congress 2022 in Granada.

The results show that while these planets are 80% land-covered and 20% water, less than 1% of the exoplanets had an Earth-like climate of land and water.

“Earth-like” exoplanets

Exoplanets exist outside of Earth’s solar system, with the first discovery dating back to 1917. Current data suggests there are over 5,000 in 3,804 planetary systems, some with more than one planet.

Scientists estimate that there are about 11 billion potentially habitable planets throughout the Milky Way, rising to 40 billion if you include the planets orbiting red dwarfs.

Astronomer Carl Sagan previously suggested that researchers should look for a “pale blue dot” with Earth-like characteristics. However, the new study concluded that dry, cold “pale yellow dots” better represent extrasolar planets. The researchers also concluded that hunting for such exoplanets would result in a better probability of detection.

Professor Tilman Spohn, Executive Director of the International Space Science Institute, said: “We Earthlings enjoy the balance between land and ocean on our home planet. It’s tempting to assume that a second Earth would be just like ours, but our modeling results suggest that’s probably not the case.”

Similarities and differences between planets

Models created by the team suggest that an exoplanet’s average surface temperature is similar to Earth’s, with a deviation of about five degrees Celsius, but the main difference lies in the land-water distribution.

An oceanic planet with less than 10% land is likely wetter and warmer than Earth, reflecting the balance on our planet before the asteroid impact that killed the dinosaurs.

The land-based exoplanets with less than 30% oceans would have colder, drier, and harsher climates. The interior parts of the country are likely to be occupied by frigid deserts that mirrored Earth’s climate during the last ice age, during which extensive ice sheets and glaciers developed.

Overall, the climate of the exoplanets turned out to be much harsher than the balance on Earth today. Our planet’s climate is reasonably balanced, with continents growing from volcanic activity and eroding over time from weathering.

The process of photosynthesis allows life to thrive on Earth, where there is direct access to solar activity and the oceans are a vast reservoir of water. This increases precipitation and prevents the current climate from becoming too dry.

“In the engine of Earth’s plate tectonics, internal heat drives geological activity such as earthquakes, volcanoes, and mountain building, and leads to the growth of continents. Land erosion is part of a series of cycles that exchange water between the atmosphere and the interior. Our numerical models of how these cycles interact show that Earth today may be an extraordinary planet and that the balance of the landmass may be unstable for billions of years. While all of the modeled planets could be considered habitable, their fauna and flora could be quite different,” Professor Spohn concluded.