By human standards, Venus is not a nice place. It’s a toxic, super-heated hellscape for a world named after a Roman goddess of love and beauty. But it wasn’t always like this.
In a study, scientists make the case for how ancient Venus could have once supported life alongside oceans of liquid water, until a mysterious resurfacing event took all that away about 700 million years ago.
“Our idea is that Venus may have had a steady climate for billions of years,” says NASA’s Goddard Institute for Space Studies planetary scientist Michael Way.
“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 research, which was presented at the EPSC-DPS Joint Meeting 2019 in Geneva, Switzerland, utilizes two previous studies by Way and his team, as well as related papers modelling virtualised Venus-like planets and topographies.
The upshot, the team says, is that 3D GCM (general circulation model) mathematical modelling supports the ‘optimistic’ view that Venus “spent most of its history with surface liquid water, plate tectonics, and subsequently a stable temperate climate akin to that of Earth through much of its own [history]”.
This would have been the case for at least 4.2 billion years, up until roughly 700 million years ago. Something happened on Venus about that time, and the planet has been extremely hot ever since, with a toxic, heat-trapping ‘greenhouse effect’ atmosphere dominated by carbon dioxide and nitrogen.
This atmospheric composition is a big part of the reason behind Venus’s extraordinarily high temperatures and atmospheric pressure; but how did Earth’s ‘sister’ planet get this way?
“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 says.
“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.”
Of course, we can’t say for sure that Venus did host life based on the new research. Based on the potential for liquid water and a forgiving atmosphere, modeling suggests the planet may have once been ideal for life.
We don’t know exactly what happened. According to the researchers, an Earth-like carbonate-silicate cycle (in which CO2 is naturally removed from the atmosphere by being absorbed into rocks) was interrupted on Venus, possibly by a period of intense volcanic activity, with magma solidifying on the planet’s surface, suspending the cycle, and preventing the gas from being reabsorbed.
If they’re right, it not only means Venus could have once sustained life, but it also suggests that planets like Venus, which are typically thought to be livable due to their near closeness to their host stars, may not be quite as barren after all.
“Our models show that there is a real possibility that Venus could have been habitable and radically different from the Venus we see today,” Way says.
“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.”
The results were presented at the 2019 EPSC-DPS Joint Meeting.v