Was Venus habitable? | Space

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Artist concept of an ancient planet Venus, with a shallow ocean. Image via NASA.

The second planet outside our sun – Venus, named after the Roman goddess of love – has a size and density close to that of the Earth. But it's an infernal place, with dense clouds of carbon dioxide linked to sulfuric acid. Its surface pressure is 90 times that of the Earth and its surface temperatures are hot enough to melt the lead. Yet at the international meeting of astronomers in Geneva, Switzerland, last week, NASA's Michael Way presented a very different vision of Venus. He said on September 20, 2019 that new research reveals that Venus may have already been a temperate world, more like Earth, with a shallow ocean of liquid water on its surface for about 2 to 3 billion d & # 39; years. The new research suggests that, only 700 million years ago, a dramatic transformation began for Venus, resurfacing at about 80% of our brotherly world. These scientists said in a statement that their study:

… Gives a new vision of the climatic history of Venus and can have consequences on the habitability of exoplanets in similar orbits.

This is not the first time scientists have considered liquid water on Venus. NASA's Pioneer-Venus mission – which visited the planet 40 years ago – revealed tantalizing allusions to a long-lost shallow ocean. To see if Venus could have had a stable climate able to withstand liquid water, Way and his colleague Anthony Del Genio created five different computer simulations of Venus in the past. Each assumed a different level of water coverage. In the five scenarios, these scientists discovered that Venus was able to maintain stable temperatures between a maximum of about 122 degrees Fahrenheit (50 degrees C) and a minimum of about 68 degrees F (20 degrees C). for about three billion years.

Warmer than the Earth, certainly, but far from the average temperature of 462 ° C (865 ° F) on Venus today. If one of these scenarios describes something that looks like Venus in the past, what has happened to change things?

This modified image is based on the very first image of the surface of Venus, restored by the Soviet probe Venera 9 in 1975. The air hard, is not it? Image via Venera 9 and Ted Styrk's blog. Learn more about this image of the Planetary Society.

According to these scientists, Venus may have conserved its temperate climate until today, without a series of events that caused the release or "degassing" of carbon dioxide stored in the rocks of the planet about 700 to 750 million years.

As we should all know now, carbon dioxide is a greenhouse gas: it traps heat.

The cause of this degassing is a mystery, said these scientists, but this could be related to volcanic activity on Venus:

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 resulted in extremely high average temperatures at 462 degrees currently found on Venus.

Made it happens? Was Venus more temperate in the past? We do not know. Such computer simulations do not show what made to arrive, but what could happen. Scientists have recognized "two major unknowns:"

The first relates to the initial cooling rate of Venus and its ability to condense liquid water to the surface. The second unknown is whether the global resurfacing event was an isolated event or simply the last in a series of events dating back billions of years in the history of Venus.

Although we have not yet found an active volcano on Venus, we know that Venus has volcanic features and volcanoes have been active recently in geological terms for several million years. In fact, at the moment, we know that Venus has more volcanoes than any other planet in our solar system: more than 1,600 major volcanoes. Here is Maat Mons on Venus, the highest volcano in Venus, 5 miles (8 km) high. This perspective view is based on Magellan's radar images. Learn more via NASA PhotoJournal.

Way and his team also acknowledged in their statement that many researchers believe that Venus is beyond the inner limit of the habitable zone of our solar system; In other words, it has been suggested that Venus is too close to the sun to support liquid water. But the new study suggests the opposite. Way said:

Venus currently has almost twice the solar radiation we have on Earth. However, in all the scenarios we modeled, we found that Venus could still withstand acceptable surface temperatures for liquid water.

This discovery, if corroborated by other scientific work, could have implications for our understanding of exoplanets in orbit in distant solar systems. Have you heard of the Goldilocks area, or the habitable zone? This is the area around a star in which orbiting planets are able to withstand liquid water on their surface. Not too hot, not too cold, in other words. Perhaps we do not understand the real limit of the habitable zone, neither in the direction of the central star of the solar system, nor in the opposite direction, nor in both directions. Maybe our understanding of livable areas needs a fit.

Of course, these scientists said, as scientists almost always say at the end of any study, that more studies are needed. Way said:

We need more missions to study Venus and gain a more detailed understanding of its history and evolution.

However, our models show that there is a real possibility that Venus is habitable and radically different from the Venus we see today. This opens up all kinds of implications for the exoplanets present in what is known as the "Venus Zone", which can in fact host liquid water and temperate climates.

Venus is the brightest planet visible in the earthly sky. Only the moon overtakes him at night. Our friend Jenney Disimon caught the moon and Venus on June 2, 2019, from Kota Kinabalu, Sabah, N. Borneo. The extreme brightness of Venus comes in part from its highly reflective clouds, which retain heat near the planet, raising temperatures. Learn more about when we could see Venus in our sky again in the EarthSky Planet's Monthly Guide.

In the end: Venus is a hellish world today. Has it ever had a stable climate or liquid water? To find out more, the scientists created a series of 5 simulations assuming different levels of water coverage. In the 5 models, Venus maintained moderate relativistic temperatures for about 3 billion years.

Via Europlanet Society