Everyone wants to get off our planet Earth and explore the solar system, without realizing just how good everything is down here. Lots of air, more liquid water than we know what to do with, strong and sturdy planetary magnetic field that protects us from cosmic radiation, and nice strong gravity.
Earth is pretty nice, but we still look to our planetary neighbors for places to visit and maybe even inhabit. Mars top the list but what about Venus? With the same size as the Earth and the same mass. It’s, in fact, a little bit closer than Mars and definitely warmer than Mars. But we don’t try going for our sister planet instead of the red one because Venus is basically hell.
It’s difficult to not exaggerate just how bad Venus is. Let’s look at the atmosphere which is almost entirely carbon dioxide and chokingly thick with atmospheric pressure at the surface 90 times that of Earth. This is the equivalent pressure of a mile beneath our ocean waves. It’s so thick that you nearly have to swim through it just to move around. Only 4% of that atmosphere is nitrogen, but that’s more nitrogen total than there is in the Earth’s atmosphere. And sitting on top of all this are clouds made of sulfuric acid. These acid clouds are highly reflective, giving Venus its characteristic brilliant shine. The rest of the atmosphere is so thick that less than 3% of the sun’s light hitting Venus actually reaches its surface. That means there is only a vague difference between day and night.
But despite this lack of sunlight, the temperature on Venus is, in fact, hot enough to melt lead, at over 700 degrees Fahrenheit (370 degrees Celsius) on average. In some places, in the deepest valleys, the temperature reaches over 750 degrees Fahrenheit (400 degrees Celsius), which is enough for the ground itself to glow a dull red.
Venus has one of the most peculiar rotations in the solar system as it rotates backward, with the sun rising in the west and setting in the east. Second, it is incredibly slow, with one year lasting only two days. Moreover, Venus once had plate tectonics that shut off long ago locking its crust.
Straight To The Inferno
Venus is made of pretty much the same stuff as our Earth with roughly the same size and mass, scientists are pretty certain that, back in the early days of the solar system, Venus probably supported liquid water oceans on the surface and white fluffy clouds dotting a blue sky.
But our sun was different four and a half billion years ago. It was much smaller and dimmer. As stars like our sun age, they progressively grow brighter. So back then Venus was firmly placed in the habitable zone that is the region of the solar system that can support liquid water on the surface of a planet without it being too hot or too cold.
But as the sun aged, that habitable zone steadily shifted outward. And as Venus came near the inner edge of that zone, things started to go haywire. As the temperatures surged on Venus, the oceans began to evaporate, dumping loads of water vapor into the atmosphere. This water vapor was very good at trapping heat, which consequently increased the surface temperatures, and caused the oceans to evaporate even more, which instigated even more water vapor to get in the atmosphere, which trapped even more heat, and so on and so on as events spiraled out of control.
Eventually, Venus transformed into a runaway greenhouse with all the water dumped into the atmosphere trapping as much heat as possible, with the surface temperatures continuing to skyrocket.
The liquid water that was once present on the surface helped keep the tectonic plates nice and flexible, adding lubrication to the process of plate tectonics. But once the oceans dried up, plate activity ground to a halt, locking the surface of Venus in place. Plate tectonics play a crucial role in regulating the amount of carbon dioxide in the atmosphere. Fundamentally, carbon binds to elements in dirt and rocks, and that dirt and rocks ultimately get buried far beneath the surface over the course of millions of years as the plates rub up against each other and sink below each other.
But in absence of this process, carbon that was locked in the dirt just slowly outgassed or dumped out in massive volcanic events. So, once the oceans evaporated, the carbon problem on Venus became even worse with nothing to sequester it. Over time, the water vapor in the atmosphere got hit by enough sunlight to break it apart, sending the hydrogen into space, with all that mass being replaced by carbon dioxide rising up out of the surface.
And as that atmosphere grew thicker, the conditions on the surface became even more hellish. The thickened atmosphere might even have had sufficient drag to literally slow down the rotation of Venus itself, giving it its present-day sluggish rates. Once this process was complete, which possibly took 100 million years or so, the potential for any life on Venus was dowsed.
Sounds terrible right? But the worst part about the fate of Earth’s twisted sister is that this might be our future too. Our sun is still aging, and as it grows older and brighter, its habitable zone is steadily and inexorably moving outward. At some point in the next few hundred million years, our Earth itself will approach the inner edge of the habitable zone. Our oceans will evaporate and temperatures will spiral upward. Plate tectonics will shut off and carbon dioxide will get dumped into the atmosphere.
By then our solar system will be home to not just one hell but two.