The studies carried out on terrestrial exoplanets have highlighted that the land-water balance of the Earth is very unusual and unique to our planet.
Researchers from the International Institute of Space Sciences studied how the evolution of continents and water has shaped the development of exoplanets that exist outside our Solar System. The discovery was presented at the Europlanet Science 2022 Congress in Granada.
The results show that while these planets have an 80% chance of being covered by land and 20% water, less than 1% of exoplanets had an Earth-like climate, both terrestrial and water
“Earth-like” exoplanets.
Exoplanets exist outside Earth’s Solar System, and were first discovered in 1917. Current data suggests there are more than 5,000 in 3,804 planetary systems, some of which have more than one planet.
Scientists estimate that there are about 11 billion potentially habitable planets in the entire Milky Way, rising to 40 billion when planets orbiting red dwarfs are taken into account.
Astronomer Carl Sagan had previously suggested that researchers should look for a “pale blue dot” with Earth-like characteristics. However, the new study concluded that the dry, cold “pale yellow dots” best represented extrasolar planets. The researchers also concluded that the hunt for exoplanets like this would lead to a greater chance of discovery.
Professor Tilman Spohn, Executive Director of the International Institute for Space Sciences, said: “We earthlings enjoy the balance between land areas and oceans on our home planet. It is tempting to assume that a second Earth would be like our own , but our modeling results suggest that this is not likely to be the case.”
Similarities and differences between planets
The models produced by the team suggest that the average surface temperature of an exoplanet is similar to that of Earth, with a variation of about five degrees Celsius, but the key difference lies in the distribution of Earth’s water .
An oceanic planet with less than 10% land is likely to be wetter and warmer than Earth, reflecting the equilibrium of our planet before the asteroid impact that caused the extinction of the dinosaurs.
Earth-heavy exoplanets, with less than 30% oceans, would have colder, drier, harsher climates. The interior parts of the earth are likely to be occupied by cold deserts, which reflected the Earth’s climate during the last ice age, which saw the development of extensive ice sheets and glaciers.
In general, exoplanet climates were found to be much harsher than the current Earth’s equilibrium. Our planet’s climate is fairly balanced, with continents growing through volcanic activity and eroding through weathering over time.
The process of photosynthesis allows life to thrive on Earth, where there is direct access to solar activity and the oceans provide a huge reservoir of water. This improves rainfall 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 results in 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 today’s Earth may be an exceptional planet and that the Earth’s mass balance may be unstable for billions years. Although all the modeled planets could be considered habitable, their fauna and flora may be quite different,” Professor Spohn concluded.