All About the Planet Venus

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Podcast Transcript

As long as humans have looked up in the sky, they noticed something. There was an unusually bright star that would show up in the early morning or early evening. 

This star was one of the few points of light in the sky that moved. They were dubbed planets, and the one that appeared in the morning and evening was thought to be two different ones.

Today, we know much more about that moving star in the sky and found that it is one of the most dangerous places in the solar system.

Learn more about Venus, the second planet from the sun, on this episode of Everything Everywhere Daily.

To start any discussion on Venus, it should probably begin with why Venus is known as the “morning star” or “evening star.”

Venus is closer to the Sun than the Earth. If you can, imagine two circles to represent the orbital paths of the Earth and Venus. If you draw a line from any point on the outer circle to any point on the inner circle, it is going to have to be somewhat close to the Sun. 

An observer on Earth is never going to be able to see Venus at midnight because it has an orbit closer to the Sun. The same holds true with Mercury, but even more so because it is even closer to the Sun than Venus. 

Because Venus is much larger than Mercury, from our vantage point on Earth, it means that Venus is the second brightest object in the night sky after the Moon. 

Because observing Venus meant observing it during a very short window in the morning or evening, we didn’t know as much about it as we did for other planets, such as Mars, which could be observe in the middle of the night with longer exposures. 

As it turns out, at least on paper, Venus is the most similar planet to Earth in the solar system. 

Venus is a rocky planet about 70% the distance from the Sun as the Earth.

Venus has about 81% of Earth’s mass, and the planet’s surface has about 90% of the surface area. If you were to stand on Venus, you’d experience only 90% of the gravity that would on Earth. 

The Earth has a relatively thick atmosphere containing some carbon dioxide, and Venus has a thick atmosphere containing carbon dioxide.

The superficial similarities between the two planets end there, however. 

It is as if the Earth and Venus are like two children who were similar when they were younger, but when you see them decades later, one has become an investment banker, and the other has become a bomb-throwing anarchist. 

For starters, Venus has a very peculiar rotation. The Earth rotates about its axis once every twenty-four hours. On the other hand, Venus is the only planet in the solar system where a day lasts longer than its year. 

Venus takes only 224 days to travel around the Sun due to its proximity to the Sun and the shorter path it has to follow.  Its period of rotation around its axis takes 243 days. More on the reason why in a bit. 

Moreover, Venus rotates the wrong way. If you were to observe the rotation of every planet in the Solar System from the vantage point of looking down on the Earth’s north pole, every planet rotates counter-clockwise. 

One of only two exceptions is Venus, which rotates clockwise. (The other being Uranus). If you were standing on Venus, you’d see the Sun rise in the west and set in the east. This is known as retrograde motion.

The history of observations of Venus date back to the earliest human observations of the sky. Because Venus is so bright, with only the Sun and Moon being brighter, every culture and civilization knew about it and had a word for it. 

Most cultures didn’t know that the bright star that sometimes appeared in the morning was the same star that sometimes appeared in the evening because there would be several days between the observation of the two when the star didn’t appear at all.

Both ancient Chinese and Greek astronomers thought that they were two different stars. 

When Venus appeared in the morning, the Chinese called it “the Starter of Brightness,” and the Greeks called it Phospersus. 

The Chinese called Venus in the evening “the Excellent West One,” and the Greeks called it Hesperus.

The Roman author Pliny the Elder acknowledged that the mathematician Pythagoras thought that they were the same object, as did several other Greeks. 

The name Venus comes from the Roman goddess of love. Other cultures, such as the Babylonians and Sumerians, also used their goddess of love as the name for the planet. 

Real understanding of Venus didn’t come until the invention of the telescope. 

When Galileo Galilei turned his telescope towards Venus, he found that it exhibited phases, just like the moon did.  The phases of Venus were an important milestone in proving the heliocentric model of the solar system because Venus could only have phases if it orbited the Sun, not the Earth. 

As astronomers made more observations of Venus and as they got a better understanding of its orbit, they found that very infrequently, it would pass directly in front of the sun. An event which is known as a transit of Venus. 

A transit of Venus is the same principle as a solar eclipse, except that Venus is much further away than the moon and only appears as a dot across the sun.

The English astronomers Jeremiah Horrocks and William Crabtree predicted the first transit of Venus in 1639. 

Transits of Venus tend to occur in pairs a few years apart from each other, with gaps of over a century between the pairs. 

The transits of 1761 and 1769 were one of the first true global scientific projects, with astronomers around the world taking part. It was so important because it allowed for a means of measuring the distance from the Earth to the Sun via parallax from different observations across the planet.

There were transits in 1874 and 1882, and again in 2004 and 2012. There will not be another transit of Venus until 2117 and 2125.

In 1761, the Russian astronomer Mikhail Lomonosov discovered something that proved to be Venus’s defining characteristic. It had an atmosphere. 

The atmosphere of Venus made it very difficult to learn much about it. The rotation of Venus was an open question for a long time because no one could see the surface. There were no features on the planet that could be observed. 

Astronomers were able to eventually discern some of Venus’s secrets in the 20th century by observing Venus in the ultraviolet spectrum and by measuring the oblateness of the planet. 

Oblateness is a measure of how flat or squished the planet is. You might have heard that the Earth is actually an oblate spheroid, which means that it is ever so slightly bigger around the equator than it is around the poles. 

The oblateness of the Earth is due to its rotation. 

Venus has almost no oblateness, which was a clue to its slow rotation period. 

As the space age began, Venus was the target of several early interplanetary probes. 

The Soviet Venera 1 was the first human object sent to another planet in 1961. However, it lost contact en route, and no data was sent back. 

The first successful mission was Mariner 2 in 1962, which managed to send back images and data. 

In 1970, the Soviet Venera 7 became the first probe to do a soft landing on another planet, and in 1975, Venera 9 and 10 became the first and only probes to land on Venus and send back images of the surface. 

What was discovered from all the early probes was that Venus was perhaps the most inhospitable place in the solar system. Any thoughts about Venus potentially harboring life were quashed when it was discovered what conditions were like on the surface. 

If you were to stand on the surface of Venus, you’d die. It would only be a question of what of the many possible things on Venus would kill you first. 

The first thing that would kill you is the composition of the atmosphere. The Venitian atmosphere is 96.5% carbon dioxide, and 3.5% nitrogen, with the rest being other trace gases. So, you’d suffocate because there is no oxygen to breathe.

The next that would kill you is the incredible pressure of the atmosphere. The surface pressure on Venus is 93 bar or 1,350 pound per square inch, or to put it in terms that might be easier to understand, standing on the surface of Venus is like being 900 meters or 3,000 feet below the surface of the ocean. 

So, if you weren’t being suffocated, you’d be crushed. Oddly enough, despite nitrogen only being 3.5% of the atmosphere, there is actually four times as much gross nitrogen in Venus’s atmosphere than in Earth’s, where it makes up almost 70% of the atmosphere. 

This incredibly dense atmosphere is the reason why the planet rotates so slowly. The drag from the planet’s atmosphere has caused it to rotate more slowly. 

The final thing which could kill you on Venus is the heat. The super dense atmosphere of CO2 and its position close to the sun has led to an out-of-control greenhouse effect on the planet. 

The average surface temperature on Venus is 467 °Celcus or 872 °Farenheight. 

There are several reasons for the unique and deadly atmosphere on Venus. The first is that it is probably the most volcanically active planet in the solar system. In fact, many astronomers think that volcanoes on Venus might still be active today. 

This massive outgassing poured so much gas into the atmosphere that it led to such massive pressure.

The other big factor might have been the lack of any sort of natural magnetic field. The magnetic field on Earth protects the planet from the sun’s solar wind. On Venus, there is no protection, and most lighter gases are stripped from the atmosphere, leaving only heavier gases. 

While the surface has a high pressure, Venus has a very complex atmosphere as you go up. In fact, about 60-65 kilometers above the surface, the pressure and temperature is similar to that of Earth. 

That fact has led many people to think that floating outposts on Venus might be possible. Oxygen in Venus’s atmosphere, would serve as a lifting gas, similar to hydrogen or helium on Earth.

The hellish conditions on the surface of Venus has resulted in more attention being paid to Mars as an object of exploration, as it is simply easier to explore. If life is to be found somewhere in the solar system, it probably isn’t going to be on the surface of Venus. 

As of the date of this recording, there have been 46 missions sent to Venus, the majority of which occurred in the 60s and 70s. 

There are currently six future missions to Venus that are in the planning stages, with missions by India, the United States, Russia, and the European Space Agency. 

There has even been a proposition that we send humans to Venus before we send them to Mars. Not to land on the surface but just to do a flyby and test living in interplanetary space, something which no human has done before. 

It would be faster, easier, and cheaper than doing a flyby of Mars. 

Despite being the morning and evening star which captured the attention of early humans, Venus has actually become less alluring to researchers over time. The conditions on the planet make it so difficult to explore that it is simply easier to pick the low-hanging fruit on planets such as Mars.