March? This is old news. Welcome to the decade of Venus

When it comes to exploring the solar system, the last few decades have undeniably been focused on visiting Mars. From sending rovers to its surface to making plans for possible crewed missions, the Red Planet holds an important place in our understanding of planetary science. But what about our other planetary neighbor? Where is the love for Venus?

After decades of oblivion, three missions will soon be heading to Venus: DAVINCI + and VERITAS from NASA, and EnVision from the European Space Agency. These three missions were recently approved and aim to launch in the late 2020s or early 2030s.

This is long overdue, because although sometimes spaceships pass Venus on their way elsewhere, the last time NASA sent a mission specifically to Venus was the Magellan Orbiter launched in 1989. In the three decades that followed, the largest agency space on Earth did not visit the next planet.

To find out why and to find out what we might learn from the three new missions there, we spoke to two Venus experts: Jenny Whitten, a member of the science team for NASA’s upcoming VERITAS mission, and Jean-Luc. Margot, planetologist. who recently conducted a study on the fundamental properties of Venus.

Venus is a mystery

The first thing to understand about Venus is how little we know of the place and how many open questions remain. We do not have a timeline of the geological history of the planet, and there is no consensus on what the first Venus looked like. Compared to other places like Mars or the Moon, we don’t have a big picture of what the planet looked like over time and how it developed to state in which it is found today.

“About a billion years ago, we don’t know what was going on. There is no geological record, ”said Whitten.

We also don’t know what the planet looks like inside, which leaves many issues unresolved. “We don’t know the size of Venus’ core,” Margot said. “We don’t know if the nucleus is liquid or solid – we suspect it is liquid but we are not sure. And this drives the entire thermal evolution of the planet ”in terms of magnetic field and spin. So, “it’s really important to have a good estimate of your core size.”

Venus – 3D perspective view of Maat Mons. NASA / JPL

We know that Venus is covered with thousands of volcanoes – more than any other planet in our solar system – but we don’t know if they are active or not. “Volcanism is very important because on Venus this is how we release heat and release volatile substances from within, like water and gases that can be important for life,” Whitten explained. “So what we’re really trying to figure out with volcanic history is the habitability of Venus.”

And when it comes to the surface of the planet, there are twisted and warped regions that we’re always trying to grab hold of. “There are these strange terrains on Venus called tesserae that may be analogues of the continents of Earth, but we don’t know how they formed,” Margot said. “It is an important part of the geological history of Venus.”

A strange beast

Photo of Venus.

The second thing to understand about Venus is that it is a strange place. Its thick atmosphere is dotted with clouds of sulfuric acid, and it traps heat so effectively that it is warmer on the surface than on Mercury, although it is further from the sun. More strangely, the atmosphere turns 60 times faster than the planet below. In fact, it spins so fast that it can even affect the length of a day.

And in terms of dramatic geological events, Venus has one possibility that really takes the cake: Its surface can completely melt and reform every few hundred million years, in events called resurfacing. The theory is that the planet generates so much heat that it eventually erupts across the surface via erupting volcanoes all over the planet, melting impact craters and smoothing everything on the surface.

In an image of Magellan nicknamed the
In a Magellanic image dubbed the “Crater Farm,” we see the curious stratification of volcanic activity and impact craters. NASA / JPL

“Venus may have had a major resurfacing of the entire planet 700 million years ago,” Margot explained. “It may have had several complete resurfacing in its history, and we don’t understand how it works… It’s an episodic and catastrophic melting of the surface, which is a really fascinating process.

Earth’s evil twin

    Artist's impression of a warm and thick atmosphere rich in CO2 (left) and of today's Earth.
Tobias Stierli / NCCR PlanetS

One of the reasons researchers are so interested in Venus is that it is, on a large scale, very similar to Earth. It is comparable in size, mass and density. Venus may have already had oceans on its surface and might even have been habitable at some point in its past. It is also a rocky planet, and formed at a similar location in the solar system. This means that we can assume that the two planets are made of roughly similar material.

But today the two planets are very different. Venus’s atmosphere is overwhelmingly dense at 100 times the pressure of Earth on its surface. At 900 degrees Fahrenheit, the surface temperature is high enough to melt lead, and the planet has lost all the water it has ever had, leaving a dry and inhospitable envelope.

“There are a lot of similarities between Earth and Venus,” Whitten said. “But they evolved very differently. So we are trying to understand why.

The researchers believe that the divergence between Earth and Venus may have occurred because the higher temperatures on Venus caused more water to evaporate into the atmosphere, where it was struck by light from the sun and divided into hydrogen and oxygen. The hydrogen escaped into space, never to return, leaving the planet dry.

But that’s a guess, and we don’t know when it happened, because there is so much we don’t know about the history of Venus and how it is different from Earth. “If we are trying to understand our own planet and how the terrestrial planets evolve, Venus is really crucial,” said Margot. “And there [are] huge gaps in our knowledge and understanding.

Learning more about the differences between Earth and Venus is also important for the study of exoplanets. When we see distant planets the size of Earth, do they look more like Earth or Venus? We need to understand the evolution of planets in our own solar system to better understand what planets in other systems might look like.

An overlooked gem

Considering all the important questions about Venus that we have yet to answer, and given that this is our neighboring planet next door, you might be wondering why Venus has not been further explored. How come Mars gets all the attention?

It could be that Venus still holds clues to the possibility that life existed there at some point in her past. “And one of the biggest questions in science is about life and habitability.”

First, Venus is just very difficult to visit. To try to send a probe to its surface, you have to face extreme conditions hostile to electronics, as well as to humans. The pressure at the surface is equivalent to the pressure 900 meters underwater, “so your spaceship looks like a submarine because that’s the only way it can survive these overwhelming pressures and temperatures,” he said. said Margot. “Nothing has survived the surface of Venus for more than two hours.”

There is also our bias in terms of finding planets that appear to be able to host life as we understand it. When you look at Mars, it’s an alien place, but you can imagine people living there, albeit with carefully constructed spacesuits and habitats. Venus doesn’t look so attractive.

“For a long time, we thought Venus was inhospitable – which she is now,” said Margot. “But we didn’t realize it could have been hospitable early in the history of the solar system.”

It could be that Venus still holds clues to the possibility that life existed there at some point in her past. “And one of the biggest questions in science is about life and habitability,” Margot added.

And there might be some degree of world politics involved. “During the space race, the Soviet Union really focused its efforts on Venus, so they established a Venus program for a long time,” Whitten said. The United States, on the other hand, has focused more on Mars. Although today international cooperation in space exploration is much greater, there is arguably still a legacy of the Cold War that directs NASA to Mars and away from Venus.

But now, finally, with the three recently approved missions to Venus, we will return to this fascinating place to find out more.

“It was disheartening to a lot of planetary scientists that Venus had been overlooked for so long,” said Margot. “But now it’s really exciting that we’re finally going back.”

Three new missions

The three new Venusian explorers will be two missions from NASA, DAVINCI + and VERITAS, and one mission from the European Space Agency, EnVision. Unless you imagined there was some animosity between the rival missions of Venus, the two researchers we spoke to expressed their joy and excitement about having multiple missions to collect data. on this planet.

The three missions will be complementary: DAVINCI + will examine the atmosphere of Venus, VERITAS will examine Venus at the global level, and EnVision will image about a quarter of the surface in a much more focused way. The instruments will also be different, as EnVision has both radar imagery and a sonar to look below the surface.

“VERITAS is going to look at the deep subsoil, looking at the lithosphere,” explained Whitten. “But with EnVision, they will be able to observe the very close subsoil to understand what its structure might be.”

With the three missions combined, we should be able to learn about Venus from top to bottom, from the thick atmosphere to its deep core. Eventually, we might learn as much about this planet as we do about its best-explored sister, Mars.

“There are different goals for each of these [missions]”Said Whitten.” But overall all three of us are telling us that Venus is a key to understanding what is happening on Earth. It’s very exciting, the prospect of having a Venus program similar to a program March. “

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