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The Venusian climate has remained stable and temperate for about three billion years, until a mysterious global event resurfaces around 80% of the planet, according to a new study by NASA's planetary scientists.
The observations suggest that Venus may have had water in her distant past; A terrestrial climate model like the one above was used in a climate model to show how storm clouds could protect the ancient Venus from sunlight and make the planet habitable. Image credit: NASA.
"Our hypothesis is that Venus could have a stable climate for billions of years. It is possible that this near-global resurfacing event is responsible for its transformation from a Earth-like climate to the greenhouse we see today, "said Dr. Michael Way, of the Goddard Institute for Space Science of NASA.
In the 1970s, NASA's Pioneer Venus spacecraft discovered that the planet may have already had a shallow ocean.
To determine if the planet could have had a stable climate able to withstand liquid water, Way and his colleague, Mr. Anthony Del Genio, created a series of five simulations assuming different levels of water coverage.
In the five scenarios, they found that Venus was able to maintain stable temperatures between 20 and 50 degrees Celsius for about three billion years.
A temperate climate could even have been maintained on Venus today but there was not a series of events that caused a release of carbon dioxide stored in the rocks of the planet about 700-750 million years ago.
Three of the five scenarios assumed the topography of Venus as we see it today and considered a deep ocean of 310 m on average, a shallow water layer of 10 m on average and a small amount of water. Water trapped in the soil.
For comparison, they also included a scenario with the topography of the Earth and an ocean of 310 m and, finally, a world entirely covered with an ocean of 158 m depth.
To simulate the environmental conditions of 4.2 billion years ago, 715 million years ago and today, researchers have adapted a general circulation model in 3D in order to take into account the increase of solar radiation due to the warming of our Sun during its life, as well as the atmospheric changes. compositions.
4.2 billion years ago, shortly after its formation, Venus would have completed a period of rapid cooling and its atmosphere would have been dominated by carbon dioxide.
If the planet had evolved in the same way as the Earth over the next 3 billion years, carbon dioxide would have been sucked up by silicate rocks and blocked on the surface.
In the second model era 715 million years ago, the atmosphere would probably have been dominated by nitrogen containing traces of carbon dioxide and methane and these conditions could have remained stable until To our days.
The cause of the degassing that led to the dramatic transformation of Venus is a mystery, although it is probably related to the volcanic activity of the planet.
One possibility is that large amounts of magma bubble up, releasing carbon dioxide from molten rocks into the atmosphere.
The magma solidified before reaching the surface, which created a barrier preventing reabsorption of gas.
The presence of large amounts of carbon dioxide triggered an uncontrollable greenhouse effect, which caused the torrid temperature of 462 degrees that we find today on Venus.
"Something happened on Venus where a huge amount of gas was released into the atmosphere and could not be reabsorbed by the rocks," Dr. Way said.
"On Earth, we have some examples of large-scale degassing, for example the creation of Siberian traps 500 million years ago, which is related to mass extinction, but nothing of this magnitude. It completely transformed Venus.
Doctors Way and Del Genio presented their results on September 20 at the Joint EPSC-DPS 2019 meeting in Geneva, Switzerland.
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Michael J. Way and Anthony D. Del Genio. 2019. View of the possible habitability of the ancient Venus more than three billion years ago. EPSC Abstracts 13, EPSC-DPS2019-1846-1
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