– The hypothesis of oceans on Venus evaporates
Astrophysicists from the University of Geneva simulated the planet’s climate four billion years ago.
Posted: 10/13/2021, 5:25 p.m.
Venus is sometimes seen as Earth’s evil twin. Its mass and size are comparable to that of our planet, it has an atmosphere, contains some water and is mainly made up of rocky material. But behind this encouraging picture, a hell! Extreme surface temperature and pressure, clouds of sulfuric acid, thick CO₂ atmosphere… In short, we will not be spending our next vacation there.
“Thanks to our simulations, we have shown that the climatic conditions did not allow the condensation of water vapor from the atmosphere of Venus.”
Martin Turbet, researcher at the UNIGE Department of Astronomy and member of the PRN PlanetS
Yet the star of berger was perhaps more welcoming in the distant past. Studies have indeed suggested that primitive oceans could have developed there. To find out, the European Space Agency (ESA) and the National Aeronautics and Space Administration (the famous NASA) will also send three space missions over the next decade.
With their feet firmly on the ground, astrophysicists led by the University of Geneva (UNIGE) and the pNational Research Unit (PRN) PlanetS wanted to answer the same question. How? ‘Or’ What? «We simulated the climate of Earth and Venus at the very beginning of their evolution, over four billion years ago, when the surface of the planets was still molten.», reveals Martin Turbet, a researcher in the UNIGE Department of Astronomy and a member of the PRN PlanetS, who led the team. «Due to the high temperature associated with it, the water was present in the form of steam, like in a gigantic pressure cooker.»
Scientists then studied how the atmospheres of the two planets would evolve over time. «Thanks to our simulations, we have shown that the climatic conditions did not allow the condensation of water vapor from the atmosphere of Venus.», continues Martin Turbet. Especially because of the clouds, «which preferentially form on the night side of the planet and cause a very powerful warming by greenhouse effect which prevented Venus from cooling down as quickly as previously thought». From then on, the presence of primitive oceans on Venus evaporates…
Surprise on Earth
These simulations reserved a other surprise to researchers. They discovered that it was thanks to the relatively weak radiation from the Sun in its early days that the Earth was able to cool enough for the water to condense and form our oceans. However, until now, it was thought that if the Sun’s radiation was significantly weaker than today, it would have transformed the Earth into a ball of ice and therefore would not have allowed life to settle there. . On the contrary, «it turns out that for the very hot young Earth, this weak Sun was in fact an unexpected opportunity», underlines Emeline Bolmont, professore at UNIGE, member of PlanetS and co-author of the study.
Still, these are simulations. «Our results are based on theoretical models and are an important part of answering the question of the history of Venus, but we will not be able to answer them definitively on our computers, admits David Ehrenreich, professor in the Department of Astronomy of UNIGE and member of PRN PlanetS. The observations of the three Venusian missions will be essential to confirm – or deny – our work.», the results of which can be found in the journal «Nature».
Posted: 10/13/2021, 5:25 p.m.
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