Why did the Earth become habitable, unlike its “twin”?
Thursday – 8 Rabi’ al-Awwal 1443 AH – 14 October 2021 AD
It is possible that Venus was not able to support the oceans (Archive – Reuters)
Geneva: «Middle East Online»
The researchers also determined that a similar story would have happened on Earth, too, if things had been a little different. Venus, our closest planetary neighbor, is called the “Earth’s twin”, because of the similarity in size and density between the two planets.
While Earth is a natural center for life, Venus is ill-equipped to host life with its toxic atmosphere of carbon dioxide that is 90 times denser than ours, clouds of sulfuric acid and surface temperatures of 864 degrees Fahrenheit (462 degrees Celsius) – hot Enough to dissolve lead.
To understand how these two rocky planets turned completely differently, a team of astrophysicists decided to try to simulate the beginning, when the planets of our solar system formed 4.5 billion years ago. They used climate models — similar to what researchers use when simulating climate change on Earth — to look back in time.
The beginning of Earth and Venus
Over 4 billion years ago, both Earth and Venus were covered in magma.
Oceans can only form when temperatures are cool enough for water to condense and rain over thousands of years. This is how the Earth’s global ocean formed over tens of millions of years. On the other hand, Venus has been getting hotter.
At the time, our sun was 25 percent lighter than it is now. But that wasn’t enough to help Venus cool, because it’s the second closest planet to the sun. Researchers wondered if clouds might play a role in helping Venus cool off.
Their climate model determined that clouds did contribute, but in an unexpected way. Clouds gathered on the night side of Venus as they were unable to protect the day side of the planet from the sun. Although Venus is not tidalally confined to the Sun, with one side of the planet always facing the star, its rate of rotation is very slow.
Instead of protecting Venus from the heat, nighttime side clouds have contributed to the greenhouse effect, which traps heat within the planet’s dense atmosphere and keeps temperatures high. With this consistent, controlled temperature, Venus would be too hot for rain to fall. Alternatively, water can only exist in its gaseous form, water vapor, in the atmosphere.
“The associated high temperatures mean that any water is present in the form of steam, as in a giant pressure cooker that is used for cooking,” said Martin Turbet, lead study author and researcher in the Department of Astronomy at the University of Geneva’s Faculty of Sciences and a member of the National Center for Efficiency at Research Planets, Switzerland. ».
Why didn’t that happen to Earth, too?
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 the time as it is now.
Because the Sun was dimmed billions of years ago, the Earth was able to cool enough from its molten state to form water and create our global ocean. Turbet wrote in an email that the faint young sun “was a major component of the formation of Earth’s first oceans.”
“This is a complete reversal in the way we look at what has long been called the ‘faint little sun paradox’,” study co-author Emeline Polmont, a professor at the University of Geneva, said in a statement.
She continued, “It has always been considered a major obstacle to the emergence of life on Earth. But it turns out that for a hot young Earth, this faint sun may actually have been an unexpected opportunity.”
Previously, scientists believed that if the sun’s radiation was weaker for billions of years, the Earth would turn into a snowball. Instead, the opposite was true.
The results show a variety of ways in which rocky planets in our solar system have evolved.
The Earth’s ocean has been around for nearly 4 billion years. There is evidence that Mars was covered in rivers and lakes from 3.5 billion to 3.8 billion years ago. Now it seems unlikely that Venus supported liquid water on its surface.