Discover more about the hellish world often described as Earth’s evil twin
Imagine, in a couple of billion years, Earth’s atmosphere becomes so thick that the planet increasingly heats up. Our oceans begin to boil, life struggles to survive, and the ground turns into a deathly, poisonous desert.
It sounds extreme but, that’s pretty much what we think happened to Venus, the second closest planet to the Sun after Mercury. When the planets formed approximately 4.6 billion years ago, Venus and Earth were somewhat similar – and they still are to this day. They are both rocky planets, roughly equivalent in size and mass, and have a similar chemical composition.
And, at one point in its history, we think Venus had oceans just like Earth. But unlike our planet, these oceans did not stick around long enough for
life to arise, or so we think. Instead, a combination of an increasingly luminous Sun and harsh solar wind meant that Venus went through an astonishing transformation – and it’s one that might befall us far in the future.
The result of these changes meant that the water on Venus evaporated into the atmosphere. This thickened the atmosphere, making Venus hotter and hotter, until the carbon itself from the rocks evaporated (or sublimated) into the atmosphere, mixing with oxygen to form carbon dioxide. The atmosphere got thicker, and the planet got hotter and hotter, until it turned into the world we see today. We call this a runaway greenhouse effect.
And what is that world we see today? Well, it’s a fascinating one in its own right. Venus retains that thick atmosphere, meaning its surface is obscured from our view. But thanks to a series of Russian landers in the 1960s, 70s and 80s, and subsequent NASA and ESA orbiters, we have some idea of what’s going on there.
The surface temperature on Venus is hot enough to melt lead, at more than 450 degrees Celsius on average, making it the hottest planet in the Solar System. Its surface is covered in volcanic features, and we think it may still have active volcanoes today. Winds tear around the planet at hundreds of kilometres per hour and sulphuric acid falls as rain in the atmosphere. These hellish conditions explain why Venus is known as ‘Earth’s evil twin’. If we’re not careful with our own planet, though, Venus might be a glimpse of what is to come.
So could we actually ever live there?
The short and boring answer is no. At least, not yet. On the surface, as the temperature is hot enough to melt lead, and the pressure is 90 times as strong as that on Earth, you would be crushed to a sizzling pulp in seconds.
However, supposing that in the future we can overcome these problems, then what could we expect? Well, the surface is completely dry, although we think there may still be active volcanoes in places. The gravity, at 91 per cent, is also comparable to that on Earth. The air is so thick, though, that moving around would feel like pushing through water.
And the surface would be a strange place. Aside from the alien environment, the Sun would rise in the west and set in the east due to Venus’ backwards rotation. And the sky would be an orange-red, rather than blue like on Earth.
But while we can’t live on Venus, we could live above it. About 50 kilometres above the surface, the pressure and temperature is similar to that on Earth. All we’d need would be breathing suits to survive the sulphuric acid. Theoretically, humans could live on floating cities here. We just don’t quite have the technology – or desire – to do this yet.
This article was first published in How It Works issue 90: the latest issue of How It Works out now! Written by the How It Works team.
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