Planet Venus: The hope of a new mission in the world of the greenhouse

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NASA

Scientists say that Venus is geologically dead for a long time is a "myth".

And new research may be about to end this perception forever.

Evidence of ongoing volcanic and tectonic activity (activity in the planet's envelope) suggests that although different from Earth, the planet is very much alive.

Now scientists are building new stories to explain the landscape of the planet.

This includes an idea that proposes the existence of "caramel planets". This theory integrates the knowledge accumulated during the study of exoplanets.

The new ideas were discussed here at the 50th Global and Planetary Science Conference (LPSC) at The Woodlands, Texas.

Astronomy missions

The focus on Mars in recent decades has transformed our vision of the geology of this planet.

Meanwhile, researchers studying the surface of Venus have relied heavily on data from Magellan – a NASA mission that ended in 1994. A European mission, Venus Express, and a Japanese spacecraft, Akatsuki, are present since then, but they are both focused on atmospheric science.

After years spent thinking that a new mission would never happen, it seems like the wind is finally turning.

The European Space Agency (Esa) is evaluating a Venus mission, dubbed EnVision, alongside two astronomical proposals – Theseus and Spica. Other concepts are also offered to NASA.

Early career researchers are now choosing to join the field again in number. And scientists from other disciplines bring their expertise and bring new ideas.

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NASA

Venus is a greenhouse world, with a surface temperature of 500 ° C – hot enough to melt the lead. But it's not just the heat that makes it inhospitable: the thick atmosphere of the planet has resulted in surface pressure of up to 90 bar. This is the equivalent of what you would do at 900 m under the sea.

But Venus and Earth started to be much more similar. "They have probably already started as twins, but they have diverged," said Dr. Richard Ghail of Royal Holloway, University of London, who is EnVision's lead investigator.

"The Earth at that time has gained oxygen and life and has, essentially – a pretty cold climate, while Venus has been getting hotter and dryer over a long time."

Lost water

Like Mars, Venus may have had the right conditions in the past for life. But Dr. Ghail said that if the red planet had been able to host large expanses of water on its surface for about 100 million years, Venus could have harbored more than one billion oceans of water. 39 years in his debut.

How and when he lost this water is just one of the headaches that scientists want new missions to illuminate. His fate could even be an extreme future for the Earth.

The history of Venus exploration with robotic probes goes back more than 50 years. If the United States became synonymous with Mars exploration, it was the Soviets who scored their closest neighbor in the 60s, 70s and 80s.

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NASA

They have launched nearly 30 probes to the planet, with several notable failures. But successful missions returned crucial data, including images of the surface. One probe detected what could have been a lightning bolt, while others analyzed rock samples, which turned out to be basalts – similar to the general types found on Earth.

Part of the renewed interest in Venus is related to the type of geological activity underway and what this might tell us about rocky planets in general.

Tectonic activity

Venus is thought to lack plate tectonics, a process responsible for recycling the Earth's crust. But the idea that Venus is essentially "dead" since a wave of volcanism hundreds of millions of years ago is wrong in the eyes of a growing number of researchers.

Venus has many signs of tectonic activity on Earth, such as networks of ridges and faults.

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NASA

Mr. Ghail has identified signs that the Venus crust is divided into blocks 500 to 1,000 km wide, which move slowly in the same way that the pack ice floats on an ocean, pushing and rubbing against each other. others. The process is conducted by convection (the process of heat transfer that pushes the hottest materials upwards and the coldest and densest materials downwards) into the mantle region below the crust.

"They are moving in the block next to them, and so on.You can connect these elements and see that everything is heading towards Ishtar in the northern hemisphere," said the Royal Holloway researcher at BBC News .

Ishtar Terra is one of the main mountainous regions of Venus, sometimes described as a "continent".

"I think you take enough ice, put it in the same place, thicken it and make a big plate," said Dr. Ghail.

Caramel planet

Dr. Paul K Byrne, of North Carolina State University, believes that this idea would fit well with a theory he developed on the relationship between the thickness of the lithosphere, the rigid envelope of a planet and its gravity.

"The basic idea is this: because in a world where gravity is low, you could get a thicker layer, we thought that if you had a higher gravity, like a Super Earth (a planet class of average size seen around other stars but not in the solar system) – then this fragile layer would be proportionately thinner. "

It calculates that particular combinations of planetary mass, atmospheric pressure, and composition, as well as the distance from a planet to its star, can produce what is called a caramelized planet, where the lithosphere is very thin.

"For example, one of the ways that lava could appear is that the magma goes up to a certain depth and makes its way through fractures or dikes, but if you do not have a thick layer … it will not come not in this is an easy and enjoyable way.This could happen in a larger mass, but it will not be focused and you do not expect to find chains of volcanoes, "explained Dr. Byrne.

Regarding Venus, he said: "Some parts of Venus could be quite thick, but some parts of Venus, in the lowlands, the fragile layer could be very thin."

According to this scenario, the idea of ​​crustal blocks moving like pack ice becomes plausible, said Dr. Byrne. If this option is selected, EnVision will be equipped with a synthetic aperture radar to test some of these ideas.

"I think this is happening, other people think nothing is happening, the other possibility is that it's really Earth-like and really active … the only way to distinguish between these is with radar – Venus radar observation. "

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