A new study using a latest-generation climate model says Venus could never have had oceans.
According to Bordeaux astrophysicist Jérémy Leconte, the atmosphere of Venus has never been able to cool enough to generate rains and form oceans.
On the other hand, the Earth benefited from its formation of insolation 30% less than it is today, which allowed the formation of oceans on its surface.
Particularly hostile with temperatures reaching 450 ° C, could the planet Venus benefit from a milder atmosphere when it was created? Has it ever sheltered oceans? If an American study hypothesized that yes, it is now contradicted by work to be published this Thursday in
after a study piloted by the University of Geneva and involving scientists from the CNRS and the University of Versailles Saint Quentin 1 (UVSQ) and the Bordeaux Astrophysics Laboratory.
Venus would never have had oceans, this is the conclusion of a study published today in Nature and in which Jérémy Leconte from LAB participated.
This work also shows that the Earth owes its habitability to the initial low luminosity of the Sun.
- LabAstroBordeaux (@LabAstroBord) October 13, 2021
Thanks to a latest-generation climate model, the research team established a different scenario from the American study, the first results of which were presented in 2016.
interviewed Bordeaux astrophysicist Jérémy Leconte, researcher at the CNRS, which participated in this study.
How did you come to the conclusion that Venus never sheltered an ocean, thus contradicting the American study?
We don't really contradict her, but her initial assumption does not apply.
She had simulated the presence of oceans on Venus, with the aim of determining if these oceans could have been maintained over time, concluding that it had.
We wanted to know if these oceans could simply have formed, and it is not.
And what is it that allows you to come to this conclusion?
For this we have developed a climate model, which has already served us in the past to work on other studies, allowing us to recreate the initial climatic conditions of Venus, 4.5 billion years ago. A planet that forms is a meeting of rocks and asteroids that fall on each other, and which first create a protoplanet, made up massively of molten lava. A fairly thick atmosphere covers this molten lava, and plays a fairly strong greenhouse effect. The question was whether this atmosphere was able to cool enough to generate rains and form oceans? And that's no. Our climate model showed that water clouds did form, but almost exclusively on the night side of Venus. As a result,these clouds did not make it possible to reflect the sunlight to cool the planet, on the contrary they had a very important greenhouse effect and played a role of heat shield which prevented the atmosphere from cooling.
What explains why on Earth we could have had rains which formed the oceans, and not on Venus?
The Earth being further from the sun, it received less energy and was able to cool itself.
Did the climate model you developed teach you anything about Earth as well?
The Sun was 30% less bright at the start of Earth's life than it is today.
We saw this as a problem for a long time, because we had to explain why the Earth was not frozen, but in fact it was an opportunity that saved the Earth.
If the Earth had received the sunstroke it receives today, it would have been like Venus, that is, it could not have cooled, and the oceans would not have been able to form. .
This is also quite new.
You had already worked a few years ago with this same climate model, on the issue of ocean evaporation?
Yes, in 2013 we published a study to find out when the oceans on Earth would evaporate.
At the end of its life, the Sun will be 30% brighter than it is today and the Earth's oceans will evaporate, within a billion years, when the temperature on the Earth's surface reaches around 1,000. ° C ...
Let us return to Venus.
What is the program of the space missions to Venus, and should they confirm your study?
Three space missions - two American and one from ESA - on Venus were selected and should be launched in the late 2020s, early 2030. Measurements of the isotopic composition of the atmosphere should be carried out, to find out if some water has evaporated from the atmosphere into space, and when.
There will also be analyzes by radar data of the composition of the surface of Venus, to find out if this planet is more basaltic, or granitic like what we have on our continents, the latter type of rock requiring the presence of liquid water for a very long time ...
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