Fire of life?

Venus - a planet that's often been described as Earth's twin.

In fact, it was once believed that Venus could share more than just its size with Earth, and many thought that it could harbour a lush paradise behind its incredibly thick clouds.

See, the problem with Venus was and still is that its extremely thick clouds prevent any kind of satellite or telescope from identifying anything on the surface, making it until recently, relatively unknown what lied exactly beyond the atmosphere.

Therefore, it could only be assumed that based on its size, which is very similar to that of the Earth and distance from the Sun, it could very well have similar properties to that of our planet, with the primary one being liquid water.

However, we've learned a lot since then...

Here's a simulated image of Venus, which at least gives a good illustration of the thick clouds that prevent any kind of surface from being seen.

If Venus is Earth's twin, then it's one hellishly dissimilar twin, perhaps an Evil twin.

By now, you've likely heard of a process called the "greenhouse effect" which has gained a lot of attention in the recent years as scientists propose that it's causing the Earth's surface temperature to rise, resulting in the melting of icecaps and subsequent rise in sea level.

Now you might be wondering why I've randomly brought that up, after all, we are here to talk about Venus! Well this process is also present on Venus, but to an extreme - I mean far beyond that of the Earth's greenhouse effect.

We now know that the surface temperature of Venus is roughly 390 degrees celsius!

And it's theorised that 370 degrees of this can be attributed by the greenhouse effect - meaning that it might have a similar temperature to Earth if it wasn't for its carbon-dioxide rich atmosphere (we'll talk more about that in a minute) preventing the radiation that goes in from going back out.

The atmosphere

To talk more about this, because our atmosphere is comparatively thin, although thick enough to retain liquid water and the like, much of the sunlight that comes in, goes out.

However, Venus' extremely thick atmosphere causes much of the sunlight to be absorbed and retained by carbon dioxide in the atmosphere, which is what drives this incredible "humidity", if you like.

It can't be stressed enough - the atmosphere on Venus is extremely dense.

To put it into perspective for you, the atmospheric pressure of Venus is roughly 95 times that of the Earth's.

That is an incredible amount of pressure...

You might be interested to know that here on Earth, every square inch of your body feels about 14 pounds or 6kg of force from the atmosphere!

But why don't you feel like you're being crushed?

Well, because fortunately the pressure inside of your body is roughly the same as this pressure from the atmosphere, so the force pushing out on your body is roughly the same as the force pushing against you, hence they cancel each other out - an potential example of Darwin's theory of evolution.

But on Venus?

95*14 = 1330, so 1330 pounds of force

Well, you'd be crushed that much is for sure.

In fact, all the satellite probes that make it through the atmosphere and onto the surface have a record survival time of just 1 hour before being crushed, and that's metal... I wouldn't fancy my chances put it that way, and that's if I haven't melted already from the 390 degrees Celsius heat!

So why is Venus' atmosphere so dense?

It's attributable to a few different factors, with the 2 biggest ones being:

• It's 98% Carbon dioxide (the atmosphere on Earth is only circa 2%), and;

• the massive volume of water vapour in the atmosphere.

Carbon dioxide is prone to absorb the radiation from the Sun, stopping it from being reflected back off the surface and returning to space. This creates a lot of heat, but on top of that, the sheer quantity of water vapour does the exact same thing and just warms the planet up even more.

Perhaps Venus once had oceans... nobody knows... which quite frankly is something that you'll often hear me say at Expansive, because it's true - most of the universe is completely unknown to us, but we can do our best to formulate the most accurate predictions.

Raining acid...

Additionally, there are also traces of sulphur dioxide in the upper atmosphere of Venus, which reacts with the abundant supply of water vapour to form sulphuric acid...

I'm sure you've heard of that one before and it's not good news...

It means it essentially rains acid on Venus, and not slightly acidic water like here on Earth. It should also be recognised that the intense heat and pressure results in never ending thunderstorms on the Venusian planet.

The surface is also riddled with volcanoes, many of which are thought to still be active today.

We've covered the general fundamentals of the planet's atmospheric composition and primarily its effect on the climate of the planet, but let's zoom out a bit and talk about the planet as a whole.

Back to the basics

So I mentioned earlier that it's of a similar size to Earth, which is true. Its diameter is about 12,100km which is very comparable to the Earth's 12,700km.

Its average distance from the sun is 62 million miles, which is also comparable to the Earth's 92 million miles.

Similarly, which I forgot to mention earlier, Venus is in fact considered to be the closest planet to the Earth, despite common assumptions that Mars is the closest, which I think probably just stems from it being more talked about in terms of possible, future commercial travel!

But that's simply because, and I'm sure you'll be aware of this by now, Venus is just an absolute nightmare of a planet and no human could feasibly survive for any significant time period, at least not in the near future.

There are a few more peculiarities with Venus though...

Spinning the wrong way (if there is such a thing as the "wrong" way)

It's the only planet in the Solar System that rotates retrograde, or in other terms clockwise, with every other planet (except Uranus which rotates on its side!) rotating anti-clockwise.

In addition to this, its rotational velocity is extremely slow (relatively speaking) , with its day lasting even longer than its year!

It takes so long to complete a single rotation (which the Earth can do in 24 hours) that it completes a revolution around the sun in less time.

To throw some numbers at you, it takes Venus about 243 Earth days to rotate on its axis once, and about 225 Earth days to complete an orbit around the Sun. Notice how I specifically say "Earth days", as,by definition, it actually takes Venus less than 1 day to go around the Sun, since we've just established that its days are longer than it's years.

So why does Venus take so long to rotate on its axis?

Currently, it's understood that it's mostly because of it's incredibly high air pressure as we've already discussed. There are two main forces at play here that dictate the planet's rational velocity:

• the gravitational force from the Sun, and;

• the frictional force of the atmosphere.

Simply put, you could say that Venus has "so much atmosphere" (ie there are so many particles that make up its atmosphere) that it's frictional force on the planet is comparable to the force that's applied from the Sun.

Gravity wants to turn it one way, and the atmosphere wants to turn it the other way, and they're both similar in terms of the strength, hence they almost cancel each other out.

I think we'll conclude it there as I don't think listing every last detail however small is that helpful. Just remember that Venus is far from a paradise as astronomers once suspected it to be, and is commonly referred to as Earth's Evil Twin.

Anywhere but there, Ryu...