Venus May Have Once Boasted Earth-Like Temperatures, Oceans and Even Life

The planet of Venus as captured in visible light. Carl Sagan first posed a question about what could survive in the clouds of Venus, which have more favorable conditions than the surface of the planet. (Photo: NASA)

It may look like a classical depiction of hell today, but Venus used to be a very different planet.

In fact, a new study suggests the second planet from our sun basked in downright Earth-like temperatures for billions of years, even boasting oceans of liquid water.

That is, until about 700 million years ago, when a mysterious event poisoned the atmosphere and transformed Venus into a poster child for runaway climate change.

"Our hypothesis is that Venus may have had a stable climate for billions of years," lead author Michael Way a planetary scientist at NASA's Goddard Institute for Space Studies, notes in a statement.

"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."

The study was presented at the 2019 joint meeting of the European Planetary Science Congress (EPSC) and the Division for Planetary Sciences of the American Astronomical Society (DPS) in Geneva, Switzerland. It incorporates previous research conducted by the same team, as well as computer models of Venusan worlds and topographies.

"Venus currently has almost twice the solar radiation that we have at Earth. However, in all the scenarios we have modeled, we have found that Venus could still support surface temperatures amenable for liquid water," Way explains.

Where things went wrong for Venus

This false-color view of impact craters on the surface of Venus reveals what the surface looks like underneath the clouds. NASA/JPL

How does a planet go from mild mannered to enfant terrible in such a relatively short span? Scientists still don't know the specifics, but suspect a mass outgassing of carbon dioxide spoiled the postcard-perfect scenery.

(All right, so Venus still makes for a pretty postcard, as you can see here. But more like the kind you might pick up at the gift shop in hell.)

"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 explains in the release. "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."

Those epic volcanoes studding the Venusian landscape may be the obvious culprits, capable of spewing massive amounts of carbon dioxide into the atmosphere in a very short time.

Whatever the cause, it resulted in temperatures skyrocketing from between 20 and 50 degrees Celsius to nearly 500 degrees today, not to mention an atmosphere that would crush visitors long before their tongues tasted a single sulfuric acid raindrop.

But before that toxic curtain was drawn around the planet, Venus may have been a good place to raise the kids for as many as 3 billion years. It featured at least three factors critical to supporting life as we know it: a mild climate, plate tectonics and that all-important liquid water.

And, considering that the oldest known fossils on Earth are roughly 3.5 billion years old, there was more than enough time for life to emerge, and even thrive, on Venus.

The blackened, scorched surface of Venus as captured by the Soviet spacecraft Venera 13 in 1981.
The blackened, scorched surface of Venus as captured by the Soviet spacecraft Venera 13 in 1981. The craft lasted about 127 minutes before succumbing to the planet's extreme surface temperatures. (Photo: Soviet Academy of Sciences)

The blackened, scorched surface of Venus as captured by the Soviet spacecraft Venera 13 in 1981. (Photo provided to NASA by the Soviet Academy of Sciences)

But if there ever was life on Venus, we're still a long way from finding any hints of it. Unlike Mars, the so-called "Morning Star" isn't even remotely viable for human exploration. Back in 1978, an unmanned spacecraft called the Pioneer Venus mission, did gather some tantalizing clues. According to NASA, Pioneer Venus set out to "investigate the solar wind in the Venusian environment, map the planet's surface through a radar imaging system and study the characteristics of the upper atmosphere and ionosphere."

Along the way, it gathered evidence that the planet had once supported a shallow ocean. Still, aside from the possibility of microbial life somehow eking out en existence there, scientists didn't immediately buy into the idea of a life-sustaining Venus. After all, prevailing theory has it that the planet orbits the sun too closely — that it lies too far outside the traditional habitable zone — to support liquid water.

That understanding of habitable orbits, or so-called "Goldilocks" zones, may be upended by the new research. It may even require a second look at planets outside our solar system that were previously ruled out for life due to their proximity to their star.

But most intriguingly, it may open the door for a closer look at a planet that's long been upstaged by Mars when it comes to finding life, past or present.

"We need more missions to study Venus and get a more detailed understanding of its history and evolution," Way adds. "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."