American researchers have determined that Venus may have had oceans and lakes up to 3 billion years ago, but much shallower than those on Earth. Credit: NASA
Venus is a literally hellish and uninhabitable planet today, but according to some studies, it once had large oceans and lakes on its surface. Maybe even life. Studying the ominous fate of Venus may help astronomers better understand the future of habitable (or potentially habitable) planets like Earth. But, what happened to the reservoirs of the so-called “planet of love”? And where did all the oxygen that should have been released into the atmosphere go? The current atmospheric composition of Venus does not explain the events unless it satisfies certain strict conditions. Through mathematical simulation, scientists have determined that if the planet ever had water on its surface, it wouldn’t have happened for another 3 billion years. In addition, the basins should not exceed an average depth of 300 m, much less than that of the Earth’s oceans. Only with these characteristics it is possible to explain the presumed past habitable era of Venus, before becoming the present extraterrestrial world.
The two American scientists Alexandra O. Warren and Edwin S. Kite, both from the Department of Geophysical Sciences at the University of Chicago, determined that Venus may have had oceans and lakes, but not before 3 billion years ago. The two researchers reached their conclusions after running a simulation of Venus’s atmospheric composition as a function of time, “beginning at the end of a hypothesized habitable era with liquid water on the surface,” as noted in the study abstract. They were thus able to calculate the rate of oxygen loss after the evaporation of the supposed lakes, concluding that to be in the current situation, the basins must have disappeared for a long time. The result of this study contrasts with that of an investigation carried out by scientists from the Department of Physics and Astronomy at Uppsala University (Sweden) published in 2019, according to which Venus would have been habitable like Earth until “only” 700 million years. .
As the experts explain, the water present at the end of a habitable era “must have been lost by photodissociation and hydrogen leakage, which caused the accumulation of oxygen in the atmosphere.” But today, the atmosphere of Venus is very low in oxygen, being composed mainly of carbon dioxide (96%) and nitrogen (3%), with very small percentages of other gases. The atmosphere is so dense and corrosive that it causes the most powerful greenhouse effect in the solar system, reaching a surface temperature of 464°C at a pressure 90 times higher than that of our planet. Oxygen is very low, so that released by photodissociation was released into space or captured by oxidizable magma. Taking into account the nearly 100,000 simulations performed by scientists, performed on multiple parameters, such as current argon concentrations related to past volcanism on Venus, the scientists found that only 0.4% of the results yielded current conditions compatible with an earlier era. habitable. In short, the chances that Venus actually has liquid water are slim and subject to strict conditions. Details of the research “Narrow Range of Early Venus Habitable Scenarios Enabled by Radiogenic Argon Outgassing and Oxygen Loss Modeling” have been published in the scientific journal PNAS.
Reference:
https://www.pnas.org/doi/abs/10.1073/pnas.2209751120
Alexandra O. Warren et al, Narrow Range of Early Venus Habitable Scenarios Allowed by Radiogenic Argon Outgassing and Oxygen Loss Modeling, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2209751120 M.Turbet et al. 2021. Cloud asymmetry between day and night prevents early ocean formation on Venus, but not on Earth. Nature 598, 276-280; doi: 10.1038/s41586-021-03873-w