After Mars, Venus – SWI

After Mars, Venus – SWI
After Mars, Venus – SWI

The clouds that make Venus so bright in our night sky capture the heat it receives from the sun, creating a terrifying greenhouse effect. Average soil temperature: 460 degrees. (artistic impression) Keystone

This content was published on October 28, 2021 – 09:00

October 28, 2021 – 09:00

Marc-André Miserez

After starting my career in the regional press (print and radio) of French-speaking Switzerland, I joined Radio Switzerland International in 2000, at the time of transition when was born. Since then, I have written, and sometimes produced, short videos on all kinds of topics, from politics to economics, culture and science.

More articles by this author / this author | Writing in French

With the red planet (Mars) making headlines this year, space agencies are preparing ambitious missions to Venus, Earth’s twin planet. But what can such a hostile world teach us?

Gone are the days when science fiction authors imagined Venus to be a vast tropical swamp teeming with carnivorous plants and other strange creatures. Since the beginning of the space age, probes sent to Venus – our closest neighbor – have revealed a totally inhospitable planet: with temperatures that could melt lead or tin, an atmosphere with 96% CO2, clouds of sulfuric acid and a pressure on the surface 92 times higher than that of the Earth. Enough even to crush an armored ship like a soda can.

But if someone stays between 40 and 50 kilometers above the ground, in the upper atmosphere of the planet he will find conditions of temperature and pressure that can well be compared to those on the surface of the Earth. And these conditions are conducive for a life form to appear, even if there is not enough water.

“It is possible that the bacteria have developed there. This is still speculation, but it is not entirely unreasonable, ”says Peter Wurz, who heads the departments of Space Research and Planetology at the University of Bern. Its center has built a solid reputation in space exploration: from the Apollo 11 solar sail, to the CHEOPS orbital telescope, to the instruments on board the Rosetta probe, whose fate is forever linked to that of the comet. Chouri.

Three missions to come

But this hypothetical possibility of finding life is not the primary reason why Peter Wurz and his colleagues – from all over the world – are interested in the cloud planet. They want to know more to better understand the evolution of the worlds, also in light of the data that is beginning to accumulate on the numerous rocky exoplanets already identified in the galaxy.

After the commotion generated last spring by the arrival of several probes and two rovers – one American and one Chinese – on Mars, the American (NASA) and European (ESA) space agencies have taken turns announcing their future plans for Venus.

Venus: the return

The recognition of Venus began at the beginning of the space age. Although NASA was the first to approach Venus with Mariner 2 (1962), the Soviets were the most assiduous and the only ones who managed to land there after suffering more than 15 failures (!) At various stages of the flight to the planet. Between 1970 and 1985, ten of its machines managed to land on the surface of this infernal place, which destroyed them in a few minutes. The survival record is held by Venera 13External link, which succumbed after two hours and seven minutes.

Then the interest waned. The Soviet Union collapsed and the missions became estranged. In 2005, Europeans launched Venus ExpressExternal link and since 2015 the Japanese Akatsuki probeExternal link surrounds the planet to study its atmosphere.

End of insertion

In June of this year ESA announced the EnVision missionExternal link, whose departure from Earth is scheduled for the year 2031. After a 15-month journey and a period of another 16 to slow down and stabilize in orbit, the probe will study the atmosphere and surface of Venus through various instruments, some of them which will be provided by the US agency. NASA, for its part – and after 30 years of absence – plans two missions for 2028-2030: DAVINCI + and VERITAS, briefly described in the following video (in English).

External content

While DAVINCI + will plunge into the planet’s atmosphere, VERITAS will remain in orbit to study its geological history.

“Venus is part of the history of our solar system. All planets are made of the same basic material, so why are they so different? Why do we have life on Earth and apparently not on Mars or Venus? Today Mars and Venus are not habitable, and one wonders what went wrong during their development ”, Peter Wurz tells us.

Terrible greenhouse effect

The scientific community – the Swiss included -, based on data from previous missions, already has some ideas in this regard. A study External linkpublished in late 2020 by an international team led by Paolo A. Sossi from the Swiss Federal Polytechnic School (EPFZ) has shown that the greenhouse effect is a problem for Venus, just as it is for Earth. Paolo A. Sossi has come to the conclusion that in the early days, when their crust was still molten, Venus and Earth had very similar atmospheres, a hypothesis debated for decades.

So why can we breathe deeply in the morning breeze when the atmosphere of our neighboring planet looks more like a boiling cauldron in which the slightest immersion would kill us in a matter of seconds?

Photographed in 2006 by the Venus Express probe (200,000 km), the planet is perpetually hidden behind its clouds. Keystone

Venus is closer to the Sun than Earth, and receives about twice as much heat from the Sun. But this is not the only reason. If the second planet in the solar system is even hotter than the first (Mercury), it is largely due to a terrible greenhouse effect, much worse than the one we are experiencing with current climate change. “It is not the fault of the human being. The heating process is not linear; at a given moment it is exponential, the phenomenon spirals out of control and becomes irreversible ”, explains Peter Wurz.

And he cites an example of self-accelerating warming: on Earth, the ice at the poles reflects the sun’s rays and sends this energy into space. But when it melts, the oceans absorb the heat and the effect is amplified, even without human intervention.

Venus in a Minute – NASA

External content

Did Venus ever have oceans? On Mars the answer is obvious: surface erosion shows that large amounts of water once existed there. But on Venus, with the clouds permanently obscuring its surface, radar is needed to detect any similar markings.

This will also be one of the objectives of the three future missions that “will make available to the scientific community a powerful and synergistic set of new data to understand how Venus formed and how its surface and atmosphere have evolved over time” , as the Swiss Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate, has written.

Switzerland is on it

Another question that interests the scientific community is to know if there are still active volcanoes on Venus. A recent international studyExternal link (in English), led by geophysicist Anna Gülcher, also of the EPFZ, suggests that it is. Using new computer models, the researchers have identified a “ring of fire” on its surface, a discovery that “significantly changes the view from an essentially dormant planet to one whose interior continues to bubble and may be fueling many active volcanoes,” in their words.

In addition to carrying out these studies on the ground, the Swiss researchers will also contribute to future missions.

“There will be Swiss material on the European EnVision mission,” notes Peter Wurz. Even if it’s just the fairing of the Ariane 6 rocket, which is traditionally supplied by RUAG Space. And his institute – which was already present on Venus Express with two instruments – this time has proposed to ESA one for the analysis of the atmosphere. The physicist is confident: “The mission is not yet defined in all its details, but the world is small and we have a good reputation.”

As for NASA probes, Peter Wurz admits that even if they get regular access, the market for the Swiss is tough. “America is great, and if they have someone to do it there, they will give it to him.”

Translated from the French by Lupe Calvo

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