The researchers also determined that a similar story would have occurred on Earth, if things had been a little different.
Venus, our closest planetary neighbor, is called Earth’s twin because of the similarity in size and density between the two planets. Otherwise, the planets are radically different.
While Earth is the natural center of life, Venus is a lifeless planet with its toxic atmosphere of carbon dioxide 90 times thicker than ours, sulfuric acid clouds and surface temperatures of 864 degrees Fahrenheit (462 degrees Celsius), hot enough to melt lead. .
To understand how these two rocky planets transformed in a completely different way, a team of astrophysicists decided to try to simulate the beginning, when the planets in our solar system formed 4.5 billion years ago.
They used climate models, similar to those used by researchers in simulating climate change on Earth, to look back in time at Venus and Earth.
When Earth and Venus were ovens
More than 4 billion years ago, Earth and Venus flowed in hot tubes covered in magma.
Oceans can only form when temperatures are cold enough for water to condense and fall in the form of rain for thousands of years. This is how the global ocean of the Earth was formed for tens of millions of years. On the other hand, the flower stayed warm.
At that time, our Sun was 25% lighter than it is now. But that wasn’t enough to help Venus cool down, as it’s the second planet closest to the sun. Researchers wondered if clouds could play a role in helping Venus cool.
His climate model determined that the clouds did contribute, but in an unexpected way. They met on the night side of Venus as they could not protect the day side of the planet from the sun. Although Venus is not confined by the tides to the Sun, with one side of the planet always facing the star, its rotational speed is very slow.
Instead of protecting Venus from heat, nocturnal side clouds have contributed to the global warming effect that traps heat within the planet’s dense atmosphere and keeps temperatures high. With such constant, controlled heat, Venus would be too hot for it to rain. In contrast, water can only exist in its gaseous form, water vapor, in the atmosphere.
Martin Turbet, lead author of the study and researcher in the Department of Astronomy at the Faculty of Science and a member of the National Competition Center for Research Planets, Switzerland, said in a statement.
Why did the Earth move in the same way?
Things would have worked the same way for Earth if our planet were a little closer to the sun or if the sun was as bright at this time as it is now.
Because the Sun attenuated billions of years ago, the Earth was able to cool enough from its molten state to form water and create our global ocean. Turbat wrote in an email that the faint young sun “was an important component of the formation of Earth’s first oceans.”
“This is a total investment in the way we see what has long been called the ‘small and weak paradox of the Sun,'” Emeline Boulemont, co-author of the study and professor of the study, said in a statement. University of Geneva. But it turns out that for a very hot young Earth, this faint sun may actually have been an unexpected opportunity. “
Previously, scientists believed that if the sun’s radiation were weaker billions of years ago, the Earth would have become a snowball. Instead, the opposite happened.
The results show a variety of ways in which the rocky planets in our solar system have evolved.
The Earth’s ocean has existed for almost 4 million years. There is evidence that Mars was covered by rivers and lakes from 3.5 billion to 3.8 billion years ago. It now seems unlikely that Venus had liquid water on its surface.
outside our solar system
The new research can also be applied to exoplanets (planets outside our solar system).
“Our results have powerful implications for exoplanets, as they indicate that a large portion of the exoplanets that were once thought to have surface oceans of liquid water have now dried up because they never managed to condense and thus form. its first oceans, ”Turbet said. .
Future missions to Venus could help prove the theory presented by Turbet and his team.
“Our results are based on theoretical models and are an important component in answering this question,” he said. “But observations are needed to make a definitive judgment! We hope that future Envision, VERITAS and DAVINCI + space missions will give us a definitive answer.”
The missions of NASA and the European Space Agency, the launch of which is scheduled for the end of the decade, will help scientists understand the oldest surface features of Venus called tiles, which “may contain evidence of past traces of the presence (or absence) of liquid water on the surface of Venus, “Turbat said.