Venus is the second planet in the Solar System in order of distance from the Sun, and the 6th largest in both mass and diameter. It owes its name to the Roman goddess of love.
Venus orbits the Sun every 224.7 Earth days. With a rotation period of 243 Earth days, it takes longer to rotate around its axis than any other planet in the Solar System. Like Uranus, it has a retrograde rotation and turns in the opposite direction to that of the other planets: the sun rises in the west and sets in the east. Venus has the most circular orbit of the planets in the Solar System with almost zero orbital eccentricity and, due to its slow rotation, is almost spherical (flattening considered to be zero). It does not have a natural satellite.
Venus is one of the four terrestrial planets in the Solar System. It is sometimes referred to as Earth’s “sister planet” because of the relative similarities in their diameters, masses, proximities to the Sun, and compositions. In other respects, it is radically different from the Earth: its magnetic field is much weaker and it has a much denser atmosphere, composed of carbon dioxide at more than 96%. The atmospheric pressure at the surface of the planet is thus 92 times higher than that of the Earth, that is to say approximately the pressure felt on Earth, 900 meters underwater. It is by far the hottest planet in the Solar System – even though Mercury is closer to the Sun – with an average surface temperature of 462 °C (725 °K).
The planet is enveloped in an opaque layer of clouds of sulfuric acid, highly reflective for visible light, preventing its surface from being seen from space. Although the presence of liquid water oceans on its surface in the past is assumed, the surface of Venus is a dry, rocky desert landscape where volcanism is still taking place. The topography of Venus presents few high reliefs and consists essentially of vast plains geologically very young (a few hundred million years old).
As the second brightest natural object in the night sky after the Moon, Venus can cast shadows and can sometimes be seen with the naked eye in broad daylight. Venus being a lower planet, it stays close to the sun in the sky, appearing either in the west just after dusk, or in the east shortly before dawn. Due to its large apparent magnitude, Venus was the subject of the first astronomical observations and was the first planet whose movements were traced by Man, from the second millennium BC. She was also incorporated into many mythologies as the Morning Star and the Evening Star, and later was a source of inspiration for writers and poets. She is also known in Western culture as the “Shepherd’s Star”.
Venus was a privileged objective for the first interplanetary explorations because of its small distance from Earth. It is the first planet visited by a space vehicle (Mariner 2 in 1962) and the first where a space probe has landed successfully (Venera 7 in 1970). The thick clouds of Venus making it impossible to observe its surface in visible light, the first detailed maps were produced from the images of the Magellan orbiter in 1991. Projects of rovers and more complex missions have also been considered.
Near-global view of Venus in natural colour, taken by the MESSENGER space probe. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington, Public domain, via Wikimedia Commons
The climate on Venus
For a long time, the surface of Venus remained an enigma: it is covered by an immense cloud cover. The fact that it is closer to the Sun than the Earth could suggest that its climate is hot and humid, even tropical: ideal conditions for the appearance of life. In the 1960s, many scientists were still convinced that the climate present on Venus must be comparable to some of our tropical countries. The first images of the surface of Venus were transmitted by Venera, a Russian probe sent in the 1970s. They did not reveal a tropical Eden, but indeed a hostile desert, filled with dust and without the slightest drop of water. ‘water.
In many ways Venus and Earth are similar in composition and size, and it is highly likely that they were formed in the same gas cloud 4.5 billion years ago.
But unlike Earth, the entire Venusian surface is made up of extinct volcanoes and solidified lava. Clouds over Venus contain deadly sulfuric acid. The atmospheric pressure is 90 times higher than the Earth: if a man were sent there, he would be immediately crushed under this pressure. The atmosphere of Venus is almost entirely made of carbon dioxide. It is a greenhouse gas that traps heat. The resulting heat, is around 480 °C (896 °F), it is absolutely hellish.
In 2005, Venus Express, a European space probe launched by a Soyuz rocket, set out to conquer Venus. Her mission: to discover the reasons that led the Shepherd’s Star to experience very different conditions from her twin, Earth. The probe is equipped with cutting-edge technology that will reveal the secrets of the planet. Its first mission will be to reach the orbit of Venus. It will take five months to cover the 400 million kilometers between us.
Getting into orbit around Venus is a very high risk mission, which requires perfect acceleration and deceleration phases! If the probe goes too fast, it may get lost in space. If she goes too slowly, she may be attracted by the gravitational force of Venus and crash into it. To enter orbit, the probe will need to reach a speed of 4,800 km per hour. In April 2006, the bet was won: after long minutes of waiting, the team responsible for the project was finally rewarded, because the mission was a success.
The technology aboard the Venus Express probe has made a quantum leap since the last spacecraft sent in the 1990s. This technology now allows the probe to analyze the surface of the planet very precisely without the device needing to s ‘pose there. All previous missions had a short lifespan, as they required landing on the surface of Venus and were very quickly crushed by atmospheric pressure and eaten away by heat.
Venus Express studies the planet using infrared rays, which can pass through clouds and analyze the atmosphere. Thanks to this probe, scientists were able to establish a detailed three-dimensional map of the surface of Venus. This map allows them to research what caused such a difference with the Earth.
The fate of Venus
Venus Express shed light on the first clue behind the transformation of Venus. She has detected that particles of helium, oxygen and hydrogen are escaping into space. Oxygen and hydrogen are the building blocks for water. For decades, scientists have wondered if water is present in the atmosphere of Venus. Some even believed that oceans of water covered 90% of the planet’s surface. However, the probe detected only a tiny amount of water vapor in the atmosphere. If Venus knew oceans, they have completely evaporated.
Why have the oceans disappeared?
Because of the sun ! The solar wind is capable of devastating planets which are not protected from it. The Earth has a huge magnetic field created by molten metal that moves through the core, and protects our atmosphere from solar particles. This is the big difference with Venus, which does not have a magnetic field! She is therefore at the mercy of the Sun and constantly undergoes its anger. Scientists believe that Venus has no magnetic field due to its very low rotation (243 Earth days to rotate).
It is believed that the planet was stripped of its moisture in part due to the solar wind.
We now know that there were oceans on Venus, and that they evaporated. Once in the atmosphere, water vapor is broken down into oxygen and hydrogen by the sun’s ultraviolet rays. In a few billion years, hydrogen escapes into space and the oceans disappear… By hitting the atmosphere of Venus, the solar wind blows water molecules out of the clouds. It was the loss of water that transformed Venus from once hot and humid, now scorching and unbreathable. The greenhouse effect has increased due to volcanoes, leading to disproportionate global warming.
On Venus, it is even hotter than on Mercury, while the latter is much closer to the Sun. With its global warming, Venus represents the climatic catastrophe par excellence. It is highly likely that if the Earth had been closer to the Sun, it would look like the Shepherd’s Star.
It is believed that at the beginning of their formation, Earth and Venus were identical in all respects. They evolved differently because of their distance from the Sun. Ultimately, the Earth will go through the same process as its twin sister, as the Sun heats up. But rest assured, this should only happen in a few billion years!
An enigmatic cloud layer
The Venus Express probe revealed that the cloud layer on the planet’s surface is moving 60 times faster than Venus’ rotational speed. Clouds circle the planet in just four days. This causes storms that would be unimaginable on Earth. If the same thing happened with us, the winds would circle the Earth in 30 minutes, at a speed of 80,000 km / hour! On Earth, the atmosphere spins almost at the same speed as its rotation, while on Venus, the atmosphere does not care about the speed at which the planet spins: completely independent, it goes much faster than the planet’s rotation. .
But why this strange behavior? The cloud layer on Venus is about twenty kilometers thick. Its density is such that only a small amount of solar energy can reach the surface. It is the upper part of the cloud layer, located at an altitude of over 60 kilometers, that captures most of this energy, which then pushes the clouds at incredible speeds. The more energy clouds absorb, the faster their speed.
One of the tasks for Venus Express is to solve a puzzle revealed by previous missions: the existence of a vortex at the North Pole, similar to our cyclones. Here, a cyclone is formed by hot, humid air rising above the oceans, which the sun heats up, forming clouds. When this energy enters the low, the clouds begin to spin and form a cyclone. But Venus does not have oceans capable of fueling cyclones. The Venus Express probe spotted a double vortex four times the size of the largest cyclone on Earth. The diameter of these vortices is about 2,000 kilometers and their height is 20 kilometers. They are explained not only by the speed of the winds, but also by the rotation of the planet.
A strange whistle in the air
These strange vortices are not the only mysterious phenomena discovered on Venus. In June 2006, the Venus Express probe made a new discovery: it picks up like a hissing sound occurring intermittently in the atmosphere of the Shepherd Star. This is a brief low frequency electromagnetic interference.
Scientists recognized in this strange noise the mark of electrical activity such as lightning. The problem is, the lightning we know on Earth is powered by water (droplets and ice crystals that rub against each other, creating positive and negative charges). On Venus, solar winds blew out huge amounts of water, so scientists wondered what could be creating lightning.
There is a rather controversial theory that explains that lightning comes from sulfuric acid in clouds. Sulfuric acid clouds were formed by gas that escaped from the many once-erupting volcanoes on the planet’s surface. Fast winds are believed to be the cause of the lightning formation. They provide energy to clouds to separate electrical charges. And it is now a well-founded theory: sulfuric acid exhibits the same effects on Venus as water vapor on Earth: the friction between the acid droplets creates positive and negative charges.
The volcanoes of Venus
The Venus Express probe has revealed another mystery, that of volcanoes. A long time ago, the volcanoes of Venus emitted enormous amounts of sulfur. Scientists recently observed that sulfur concentrations are different around the world. It is only when they erupt that volcanoes spit out large amounts of sulfur. Scientists believe that volcanoes must still be active on Venus, which means it is a very much alive planet. Venus Express has revealed that 85% of Venus’s surface is covered with volcanic lava. This is very astonishing in the eyes of scientists.
Comparing with Earth, this is all the more astonishing, as volcanic activity comes from the formation of tectonic plates. However, no mission to Venus has revealed the existence of such plates: its crust is solid.
Scientists believe that at some point, when Venus’ core was no longer able to contain all the stored heat, the earth’s crust cracked all over the planet, and volcanoes roared everywhere, causing a huge resurfacing of Venus. This major change in Venusian soil is dated to about 500 million years, and took tens of millions of years to complete.
This gigantic cataclysm released an unimaginable amount of carbon dioxide into the atmosphere. Scientists noted that some rocks escaped volcanic resurfacing. They even detected that these rocks had not formed in a dry environment. On the mountains of Venus, there are therefore rocks that were formed in the presence of water: concretely, this means that they were formed millions of years ago under oceans!
Life on Venus?
To appear, life needs water and lightning. However, we now know that water was once present on Venus, as well as lightning. These elements indicate that there may already have been life on Venus. Some scientists even believe that there may still be some today!
On Earth, we have discovered the presence of microorganisms in acidic, extremely hostile environments, which suggests that it is not impossible that such microorganisms could evolve in the atmosphere of Venus.
These organisms are able to survive in sulfuric acid and at temperatures above boiling. It has even been proven that these organisms manage to live in an environment where the level of carbon dioxide is higher than that present on Venus. So it could be that some life thrives on Venus, or at least, in the clouds, because the temperature on the surface seems too high to be able to shelter life: at 50 km above the surface, the temperature is of around 80 °C (176 °F), a temperature equivalent to some environments on Earth where life thrives.
What the Venus Express mission has brought to human knowledge is extraordinary. The probe traveled 140 million kilometers around Venus for two years, and proved that Venus once looked like its sister, Earth. It then had immense oceans, a habitable climate and perhaps sheltered a form of life.
But Venus was, by its too close proximity to the Sun, doomed. As life on Earth flourished, her twin sister burned to the ground. Perhaps one day an upcoming mission will reveal to us what many have been waiting for: proof of the existence of life elsewhere than on Earth!
This planet plays a fundamental role since it governs our love life, the expression of our feelings but also our relationship to art, to aesthetics. Venus symbolizes beauty and sensuality. She can also represent the woman as someone who is sure of her charms and able to play the temptress by exploiting the weaknesses of the other. The element corresponding to Venus is Air.
When Venus has a positive influence, she brings harmony, shapes charming beings, artists but also people who shine through their sociability.
Otherwise, Mercury can stir up jealousy, indolence, a form of superficiality. It can also illustrate a certain cowardice in the face of life events.
Photo explanations: This global view of the surface of Venus is centered at 180 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan science team at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the October 29, 1991, JPL news conference. It is important to note that Venus is completely shrouded in clouds. A bright elongated region in the center is Aphrodite Terra.