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The infernal planet Venus may have had a perfectly habitable environment for 2 to 3 billion years after the formation of the planet, suggesting that life would have had plenty of time to emerge, according to a new study.
In 1978, NASA's Pioneer Venus spacecraft found evidence that the planet may have already had shallow oceans on its surface. Since then, several missions have been studying the surface and atmosphere of the planet, revealing new details about how it has moved from a "planet-like" planet to the warm, warm place. infernal that she is today.
Venus is thought to have been a temperate planet harboring liquid water for 2 to 3 billion years before a major resurfacing event about 700 million years ago triggered a greenhouse effect that made the atmosphere of the planet extremely dense and burning.
Related: What would it do to live on Venus?
Researchers at NASA's Goddard Institute for Space Studies presented a series of five simulations showing the environment of Venus according to different levels of water coverage.
The five simulations suggest that Venus could have maintained stable temperatures ranging from 20 degrees Celsius to 68 degrees Fahrenheit at 50 degrees Celsius up to 122 degrees Fahrenheit for about 3 billion years, according to a statement from Europlanet .
"Our hypothesis is that Venus could have a stable climate for billions of years," said Michael Way, one of the researchers in the study. "It is possible that this near-global resurfacing event is responsible for its transformation from a hell-like hot earth-like climate we see today."
In stable climatic conditions, Venus could have withstood liquid water and possibly allow life to be born. In fact, if the planet had not experienced the resurfacing event, it might have been able to remain habitable today, the researchers said.
However, the resurfacing event triggered a series of incidents that resulted in the release or outgassing of carbon dioxide stored in the rocks of the planet. As a result, the atmosphere of Venus has become too dense and hot for life to survive.
To create the different simulations, it was necessary to adapt a 3D model of general circulation, which represented atmospheric compositions as they were 4.2 billion years ago and 715 million years ago today. The model also takes into account the gradual increase in solar radiation as the sun warms during its lifetime.
In addition, three of the five scenarios assumed that the topography of Venus was similar to that of today. In these scenarios, the depth of the ocean ranged from a shallow depth of about 10 meters to about 310 meters, with a small amount of water trapped in the ground.
By way of comparison, the researchers also considered a scenario in which the topography of the planet would resemble that of the Earth with a deep ocean (310 m), as well as a scenario in which the entire surface of Venus would be covered from a depth of 500 feet (158 m) ocean, according to the release.
"Venus currently emits almost twice as much solar radiation as the Earth, but in all the scenarios we have modeled, we found that Venus could still withstand acceptable surface temperatures for liquid water," he said. Way in the release. However, "something happened on Venus where a huge amount of gas was released into the atmosphere and could not be reabsorbed by the rocks".
From 4.2 billion years ago, shortly after the formation of the planet, Venus would have undergone a period of rapid cooling. As the planet progressed, silicate rocks would have slowly absorbed carbon dioxide from the atmosphere and trapped it in the earth's crust.
There are 715 million years ago, the atmosphere of Venus would probably have been dominated by nitrogen containing traces of carbon dioxide and methane, much like today on the Earth . The simulations suggest that these conditions could have remained stable until now, if a massive degassing had not occurred.
Although the exact cause of degassing is still unknown, it is possible that this is related to the volcanic activity of the planet. As magma and molten rocks rose to the surface of the planet, large amounts of carbon dioxide would have been released into the atmosphere. If the magma had solidified before reaching the surface, it would have created a barrier and prevented the reabsorption of gases, the researchers said.
Similar events have occurred in the past of the Earth. For example, Siberian traps are one of the most important volcanic events in the last 500 million years. This event released toxic amounts of greenhouse gases into the atmosphere and caused mass extinction, the researchers said.
"We need more missions to study Venus and get a more detailed understanding of its history and evolution," said Way. "However, our models show that there is a real possibility that Venus is liveable and radically different from what we see today.This opens up all sorts of consequences for the exoplanets present in what is called the" Zone of Venus "actually harbor liquid water and temperate climates."
Their conclusions were presented on 20 September at the joint meeting of the European Congress of Planetary Sciences and the Planetary Science Division of the American Astronomical Society (DPS) in Geneva.
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