Venus might have been habitable 700 million years ago with temperate climates and shallow oceans

Venus might have been habitable 700 million years ago with temperate climates and shallow oceans
Venus before and afterNASA

  • A new study shows that Venus might have been a habitable planet 700 million years ago.
  • Earth’s twin would have had a temperate climate and shallow oceans.
  • This means exoplanets in the ‘Venus belt’ could also be habitable.
Venus is often called Earth’s twin since it’s around the same size and distance from the Sun. But that’s where the similarities end. Its air is toxic, and its is 90 times thicker than Earth.

That might not always have been the case. Around as 700 million years back, it’s possible that Venus had stable atmosphere and shallow oceans.

A new study based on data collected by the National Aeronautics and Space Administration’s (NASA) Pioneer 12 mission suggests that Venus was a temperate and habitable planet for two to three billion years before its current state.

This opens up the possibility that exoplanets — planets outside our Solar System — located in the ‘Venus Zone’ could also host water and have temperate climates to support life.

Using the data from the mission Michael Way and Anthony Del Genio, the authors of the study, created a series of five simulations that varied in water coverage of the planet.

Temperate vacation planet

In all the five situations, Venus was able to maintain temperatures between 50 degrees Celsius to around 20 degrees Celsius. This is a stark difference from the current sizzling temperatures that average around 462 degrees Celsius — a temperature than can melt lead.

According to the study, Venus would have undergone cooling and its atmosphere would have mostly been made up of carbon dioxide around 4.2 billion years go — just like Earth when it first started out.

If Venus followed the same pattern at Earth, its evolution over the next 3 billion years would mean the carbon dioxide would slowly disappear from the atmosphere. It would either get absorbed by the rocks or locked into the surface.

So, 700 million years ago, Venus’ atmosphere would — more or less — be similar to that of Earth. It would consist mostly of nitrogen with trace amounts of carbon dioxide and methane.

The simulations and their success also bring into question the assumption of Venus being too close to the Sun to support liquid water.

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

And, it could have stayed that way.

How Venus got so hot

Somewhere between 700 to 750 million years go, the planet’s surface released all of its carbon dioxide — and no one can definitely say why.

"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," remarked Way.

One popular theory is that there was a large volcanic eruption where massive amounts of magma bubbled up. Rocks that got in its way melted, releasing the carbon dioxide into the atmosphere.

Meanwhile, the magma solidified before reaching the surface creating a barrier between the carbon dioxide and the rocks to reabsorb the gas.

The carbon dioxide had nowhere to go, causing a runaway greenhouse effect and Venus’ resultant high temperatures.

Could humans survive on Venus?

In order to figure out whether or not Venus was truly habitable 700 million years ago, scientists still need to find out how fast the planet cooled down 4.2 billion years ago. The rapid cooling needs to have been fast enough to condense vapour to water, otherwise the oceans would never exist.

They also need to determine whether or not the global resurfacing event, volcano or otherwise, was a one-time occurrence or something that played out over the years.

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