VenusVenus was it born as a hellish planet? Or has it become so throughout its history? This is a question that torments scientists. Because behind the second hypothesis, there is the idea that Venus could, one day, resemble the Earth. And therefore present conditions conducive to the development of life.
Difficult to imagine when we observe Venus today. The surface of the planet is in fact enclosed under a atmosphereatmosphere extremely dense mainly composed of CO2exerting a pressure 92 times greater than that of the Earth’s atmosphere. Under this escapeescape of lead, the temperature rises to more than 460 °C.
Venus and Earth, two planets very similar in origin?
And yet, the idea that Venus and Earth may have been very similar when they were born is not inconceivable. The two planets indeed have the same size and the same chemical composition. In addition, during its youth, the Sun was significantly less powerful. 4 billion years ago, Venus would therefore have been in the habitable zone of the Solar System. So many elements which suggest that the planet could well have resembled Earth at first. But then, what would have subsequently led to its transformation into an uninhabitable hell?
An almost complete resurfacing that hides its ancient history
One might think that observing the surface of Venus would provide information about its past, like on Mars, where the landscape and rocks bear witness to events that occurred several billion years ago. But that’s not the case. Venus, in fact, seems to have experienced an episode of almost complete resurfacing: 80% of its surface was covered by is madeis made during a major volcanic episode which would have occurred between 300 million and 1 billion years ago, thus erasing all traces of the previous history of the planet. However, this recent volcanic episode could witness major processes that allowed the constructionconstruction of the current atmosphere of Venus. Two researchers explain that this type of event could result from a destabilization of the convective circulation within the coatcoatin response to a tectonic regime transition.
Venus, a case of tectonic regime transition which would explain its current situation
Currently, Venus does not show signs of tectonic activity comparable to that of Earth. Its crustcrustinstead of being cut into plates mobilesmobilesis stagnant. However, this may not always have been the case. Certain observations indeed suggest that the lithospherelithosphere Venusian was previously much more mobile. The region of Western Ishtar TerraTerra thus seems to have been formed by movementsmovements of convergence similar to those which led to the uplift of the Himalayas on Earth. Other regions mention the existence of ancient zones de subductionzones de subductionwhere one plate sinks under another plate. In this type of tectonic regime, the magmamagma is located at plate boundaries. But what happens if the system crashes?
THE numerical simulationsnumerical simulations carried out by the researchers suggest that on several occasions, Venus would have experienced such disturbances leading to extreme magmatic episodes which would have released enormous quantities of gazgaz in the atmosphere. The results, published in the journal Science Advancessuggest in fact that Venus would have undergone a progressive evolution of a plate tectonicsplate tectonics active to a stagnant crust and that this tectonic state transition would be the origin of its current atmosphere by degassingdegassing during multiple volcanic events. Some models also suggest that this atmosphere is rather recent and that the planet may not have yet completely completed its tectonic transition.
Venus would therefore be likely to continue to evolve in the future. It also suggests that the planet’s environment must have been quite different originally and that Earth-like surface conditions would then have been possible.
