Is Earth Turning Into Venus? | Unveiled

Is Earth Turning into Venus?

We consider Earth to be the lucky planet among those in our solar system, at least in terms of being able to harbour life. It’s in the habitable zone, it has liquid water on its surface, and it has an atmosphere to protect that surface from the many dangers of outer space. But will our planet always be the most hospitable one around?

This is Unveiled and today we’re answering the extraordinary question; Is Earth turning into Venus?

When we talk about building colonies on other planets, we almost always consider Mars first of all. If Venus weren’t such a seemingly hellish planet, however, we would probably default to it for expansion. In many ways it’s considered Earth’s twin - it’s one of the closest planets to us and is almost exactly the same size as us, too, with Venus being only 5% smaller. The general structure of both planets is roughly the same, too. Earth is a terrestrial body with a core, mantle, and crust, and so is Venus. A crucial something Earth has that Venus doesn’t, however, is plate tectonics… but there is some evidence to suggest that Venus did have active plates at one stage in its ancient history, it’s just that those became inactive because of changing conditions.

It has to be said, though, that Venus is different to Earth in almost every other way. The planet itself has a uniquely strange rotation and takes 243 Earth days on average to complete a single revolution, but that length isn’t set - it varies. Which means that scientists still have trouble agreeing on just how long “a day” on Venus actually is. But that’s not the only, or even the most prominent reason why Venus is deemed quite so uninhabitable. There’s also the fact it has an atmosphere of almost pure carbon dioxide, that it has surface pressures more than ninety times stronger than Earth’s, and that the average surface temperature of 864 degrees Fahrenheit is comfortably enough to fry the electronics onboard any of the rovers we’ve so far tried to send there.

Considering its nightmarish state, then, how is it that Venus could ever be labelled as “Earth’s twin”, at all? Well, if you go back far enough in time, it’s thought that it was once eerily like the planet that we today call home. Early in its history, Venus was thought to have both liquid water on its surface and blue skies with white clouds. It used to be well inside the habitable zone of the solar system as well, and those suspected Earth-like tectonic processes of eons ago meant that it could once recycle carbon from its atmosphere - like Earth does now. It’s thought that, at one stage, even its rotation speed was at least a little closer to Earth’s 24-hour rate… all of which has led some to suggest that Venus - a long, long time ago - could have hosted life.

The problem for Venus, however, is that our sun gets hotter as it ages. Its luminosity rises by about 10% every billion years, meaning the habitable zone gradually moves ever outwards. So, for Venus, once comfortably within the solar system’s liveable parameters, the environment became more and more hostile as time wore on. With increasing temperatures, the Venusian oceans began to boil and evaporate. The water vapor produced then became trapped in the atmosphere, and this caused the already incredible heat to become even more intense. With the planet drying out fast, that’s when scientists suspect that plate tectonics stopped which, with no natural way to recycle carbon, further accelerated the runaway greenhouse effect that Venus was experiencing. On top of all of that, the planet’s volcanoes spewed (and still spew) tons of carbon dioxide into the atmosphere… and, as the sun continued to get hotter, even the water vapor was siphoned off to leave only the carbon dioxide behind. It all happened over millions of years, but it all made for the ruthless, violent, choking conditions we see on Venus today. And, according to some projections, we could ultimately see the same fate play out on Earth.

It’s seemingly inevitable that everything that has already occurred on Venus will happen to Earth in time. And that’s because the sun is still getting older, which means it’s still getting hotter, which means the habitable zone is still expanding outwards. And seeing as Earth is the next planet from the sun, we’re the next world scheduled to be bumped out of it. We know that the sun will become a red giant in around five billion years’ time, completely engulfing Earth as it does so. But, really, our star will grow too hot for us to live here in only one billion years - that’s when it’s predicted that the luminosity increase will be too much for life on Earth to withstand. Again, the heat Earth will experience will be enough to evaporate our oceans, triggering most of the same processes that have already systematically destroyed Venus.

According to some theories, life could still exist on Venus… but if it does, it’s exceptionally hardy. More likely, if there ever was life there, it was destroyed by the rising temperatures and the clogging carbon dioxide. So, if humans are still around on Earth in a billion years’ time, they’d be subject to the same unenviable situation. In fact, over the course of those one billion years, Mars may have effectively become the “new Earth” - drawn further into the habitable zone, and potentially turned into a more liveable prospect. Another reason, perhaps, why we seem so keen to migrate to Mars before anywhere else; on a cosmological scale, it buys us a lot of time!

For the most part, we are dealing in timescales of potentially millions of years. Earth isn’t going to turn into Venus overnight. But some fear that the impact of humans on Earth could be fast-tracking the situation. Our dependence on fossil fuels has long been held under the scientific and media spotlight. By continuously releasing carbon into the atmosphere, we could be pushing Earth toward a Venus-like fate more quickly than would otherwise have happened. The current conditions on Venus took hundreds of millions of years to develop, but Earth might not be afforded so long to transition.

However, some scientists are a bit more optimistic. On the other side of the argument, Venus could have simply been unlucky in its evolution, as the rise in temperature might not have been enough to explain the evaporating oceans and overload of carbon. Instead, NASA’s Anthony Del Genio proposes that Venus might have had some other sudden, unexplained change, perhaps in its core. Or, it might have at one time been impacted by another solar system planet entering into its orbit. Both alternative situations would’ve kick-started huge, fundamental changes, for sure… But neither are scenarios we anticipate happening to Earth.

Even if Earth’s eventual fate is to become another Venus, if it’s more predictably as a result of the sun growing hotter, then we at least have time to address the problem. Relying on fossil fuels for too much longer won’t do us any good, with Stephen Hawking once saying that we’re turning ourselves into Venus with our current climate decisions. But, even beyond manmade climate change, it seems as though Earth will naturally join its twin in time - purely thanks to the sun growing inevitably hotter.

The good news is that by the time that happens, humans should be advanced enough to have evacuated Earth in search of some place new. It might be Mars, but even the Red Planet would serve only as a temporary fix. Ultimately, with our star’s habitable zone continuing to expand outward, we either need to find a way to move the planets with it, or we find a way to leave the solar system altogether. Thankfully, these seismic, cosmological changes aren’t expected to happen in the near future, but that’s why Earth actually is turning into Venus.