Earth-like exoplanets unlikely to become another ‘pale blue dot’

(ORDO NEWS) — When looking for Earth-like planets around other stars, instead of looking for the “pale blue dot” described by Carl Sagan, a new study suggests looking for dry, cold “pale yellow” worlds.

Scientists believe that such searches are more likely to succeed. According to a study presented at the Europlanet Science Congress 2022 in Granada, the balance between land and water that has helped life flourish on Earth is very rare.

A team of scientists from Germany and Switzerland, led by Tilman Spon and Dennis Hoening, studied how the evolution and cycles of continents and water can influence the development of exoplanets.

Using simulations, scientists calculated that terrestrial exoplanets have an 80% chance of being covered by land, in 20% of cases, worlds can be mostly covered by water. Only 1% of the planets had a distribution of land and water similar to that of Earth.

The team’s models suggest that average surface temperatures will not differ too much, 5°C deviations are possible, but the distribution of land and oceans will affect the climate of the planets.

An ocean world with less than 10% land mass would be humid and warm, with a climate similar to Earth’s during the tropical and subtropical era following the asteroid impact that killed the dinosaurs.

Continental worlds with less than 30% oceans will experience colder, drier, and harsher climates. Cold deserts could be located in the interior of the land, and in general they would be similar to our Earth during the last ice age, when extensive glaciers and ice sheets formed.

On Earth, the growth of continents due to volcanic activity and their erosion due to weathering are roughly balanced. Life based on photosynthesis thrives on land, where it has direct access to solar energy. The oceans are a huge reservoir of water that increases rainfall and keeps the current climate from getting too dry.

“Our numerical models show that the modern Earth may be an exceptional planet. While all the simulated planets can be considered habitable, their fauna and flora can be quite different,” said Professor Spon.

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