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Of all the planets that could have been habitable within our solar system like Earth, Venus and Mars are the two that scientists are looking at the most. And now, a pair of researchers believe Venus likely had a shallow ocean billions of years ago before catastrophe struck.
As we know it now, Venus is a planet with an atmosphere consisting of 96 percent carbon dioxide shrouded by clouds of sulfuric acid that hide the surface, which is basically a desert hell-scape marked by volcanoes.
But 2-3 billion years ago, things might have been very different, almost Earth-like.
Just 40 years ago, NASA’s Pioneer Venus mission found evidence that our “sister” planet may have been home to a shallow ocean of liquid water that made Venus habitable. If such water existed, it’s even possible that life may have thrived there before a natural disaster struck and killed everything.
This is where Dr. Michael Way of The Goddard Institute for Space Science comes in.
According to the Euro-Planet Society:
To see if Venus might ever have had a stable climate capable of supporting liquid water, Dr Way and his colleague, Anthony Del Genio, have created a series of five simulations assuming different levels of water coverage.
In all five scenarios, they found that Venus was able to maintain stable temperatures between a maximum of about 50 degrees Celsius and a minimum of about 20 degrees Celsius for around three billion years. A temperate climate might even have been maintained on Venus today had there not been a series of events that caused a release, or ‘outgassing’, of carbon dioxide stored in the rocks of the planet approximately 700-750 million years ago.
“Our hypothesis is that Venus may have had a stable climate for billions of years,” Way said. “It is possible that the near-global resurfacing event is responsible for its transformation from an Earth-like climate to the hellish hot-house we see today.”
Venus is currently the hottest planet in our solar system, yet it is only the second closest to the Sun after Mercury. But that doesn’t matter, Way says.
“Venus currently has almost twice the solar radiation that we have at Earth,” he explained. “However, in all the scenarios we have modelled, we have found that Venus could still support surface temperatures amenable for liquid water.”
But like Earth is dealing with uncontrolled greenhouse gases today, Venus went through even worse around 750 million years ago after having evolved in a similar way over billions of years.
At 4.2 billion years ago, soon after its formation, Venus would have completed a period of rapid cooling and its atmosphere would have been dominated by carbon-dioxide. If the planet evolved in an Earth-like way over the next 3 billion years, the carbon dioxide would have been drawn down by silicate rocks and locked into the surface. By the second epoch modelled at 715 million years ago, the atmosphere would likely have been dominated by nitrogen with trace amounts of carbon dioxide and methane – similar to the Earth’s today – and these conditions could have remained stable up until present times.
Venus could have been habitable, but the volcanoes intervened.
The cause of the outgassing that led to the dramatic transformation of Venus is a mystery, although probably linked to the planet’s volcanic activity. One possibility is that large amounts of magma bubbled up, releasing carbon dioxide from molten rocks into the atmosphere. The magma solidified before reaching the surface and this created a barrier that meant that the gas could not be reabsorbed. The presence of large amounts of carbon dioxide triggered a runaway greenhouse effect, which has resulted in the scorching 462 degree average temperatures found on Venus today.
It turns out we can even find instances of outgassing in Earth’s own history, which did cause an extinction level event.
“Something happened on Venus where a huge amount of gas was released into the atmosphere and couldn’t be re-absorbed by the rocks,” Way explained. “On Earth we have some examples of large-scale outgassing, for instance the creation of the Siberian Traps 500 million years ago which is linked to a mass extinction, but nothing on this scale. It completely transformed Venus.”
Could the same one day happen to Earth? Right now, greenhouse gases are causing a global temperature rise that is resulting in record heat and increased drought that will bring about desertification. It may not happen on a planetary level like on Venus, but our world is still quite vulnerable to the same disaster, only ours would be man-made instead of through a natural process.
In short, humans can actually fix our planet and reverse the damage, something that would have been impossible on Venus since the disaster was caused by volcanic eruptions. So, these simulations not only teach us about Venus, they help us learn more about own our planet and what its future could become if we don’t do something about greenhouse gases.
The research also gives scientists more reason to pay attention to exoplanets in zones similar to where Venus is located in our own solar system. Perhaps such planets could also be habitable. That means more missions to Venus should be forthcoming.
“We need more missions to study Venus and get a more detailed understanding of its history and evolution,” Way said. “However, our models show that there is a real possibility that Venus could have been habitable and radically different from the Venus we see today. This opens up all kinds of implications for exoplanets found in what is called the ‘Venus Zone’, which may in fact host liquid water and temperate climates.”
Scientists are currently developing robots that can survive longer on the surface of Venus despite the crushing pressure of the atmosphere and the intense heat. Perhaps, one day, we’ll learn more about the planet as our technology improves. That is, if we don’t learn firsthand because of how we are treating our own world.
Featured Image: Venus via Pixabay