There have never been oceans on Venus, because temperatures have always been too high to allow liquid water on the surface.
This is indicated by simulations based on atmospheric 3D models similar to those used to study climate change on Earth.
The results are published in Nature by astrophysicists at the University of Geneva in collaboration with the National Center for Scientific Research (CNRS) in France.
“We simulated the climate of the Earth and Venus at the beginning of their evolution, over four billion years ago, when the surface of the planets was still in a molten state,” explains Martin Turbet of the University of Geneva. "The associated high temperatures mean that water could be present in the form of steam, like in a giant pressure cooker." By simulating the evolution of the atmosphere, “we showed that the climatic conditions would not allow the vapor to condense in the atmosphere of Venus,” continues Turbet. “One of the main reasons is the clouds, which form preferentially on the night side of the planet”. In addition to not shielding the sun's rays,these clouds "cause a powerful greenhouse effect that would have prevented Venus from cooling as quickly as previously assumed."
Even the Earth could have known a similar fate if it had been closer to the Sun or if our star had also shone in the past as much as it does today.
This consideration overturns the so-called 'paradox of the young and weak Sun', according to which the solar radiation weaker than the current one would have transformed the Earth into a ball of ice inhospitable for life.
"Our results are based on theoretical models and are an important element in answering the question about the history of Venus, but we will not be able to pronounce on the matter definitively based on our computers," says co-author David Ehrenreich of the University of Geneva.
To verify these forecasts, the exploratory missions that NASA and the European Space Agency (ESA) are planning for the next decade will be fundamental.