After Mars and the Moon, all attacking Venus

They are twin sisters born, not under the sign of Gemini, but that of the Sun. Earth and Venus looked so similar: similar mass, size, density and orbit. Today, however, they have known radically opposed destinies. The blue planet offers lenient conditions for life when “the Shepherd’s star” is hell: arid (absence of water), Dantesque temperatures (around 460 ° C.), Oppressive (atmospheric pressure is 93 times greater than ours), rainy (sulfuric acid). Without forgetting its retrograde rotation (“upside down” in relation to our planet) at a snail speed: a Venusian day is equivalent to … 243 days with us. Hello sadness, hello boredom!

How to explain, then, that these two sisters had radically opposed destinies when many scientists believe that Venus could shelter on its surface of the oceans of liquid water and thus, perhaps, forms of life? Long neglected, the second planet in the solar system (in distance from its star) will be the star of the start of the 2030s. In quick succession, the American Space Agency (Nasa) has announced the dispatch of two missions, Davinci + (Deep Atmosphere Venus Investigation Noble gases Chemistry and Imaging) and Veritas (Venus, Radio Science Insar Topography and Spectrocopie), as part of its Discovery program and for amounts of approximately $ 600 million each.

“Incredible conjunction”

Launched in 2028 and 2030, they will begin their scientific work after 2030. The European Space Agency (ESA) has just done the same with the validation of the EnVision mission (610 million euros) which should be operational in 2035 “It’s an incredible conjunction organized by the two space agencies after thirty years of scarcity”, enthuses Thomas Widemann, researcher at the Paris-PSL Observatory and lecturer at the University of Versailles Saint-Quentin. For the astrophysicist, “Program Manager” of the EnVsion mission and who is also part of the Veritas team, there is no duplication: “They all aim to finally know the past of Venus.”

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At first glance, the latter has a much younger surface than that of the Earth (500 million years against 3 to 4 billion years). However, it does not bear any trace of recent geological activity when scientists believe that it exists. “It’s a matter of resolution. Our last images of the ground go back to the Viking probes of the 1970s and Magellan, thirty years ago, which make it possible to see it cloudy, a bit like the bottom of a swimming pool”, explains Thomas Widemann. With the Veritas and EnVision probes, scientists will finally have a more precise vision. The first will carry out an exhaustive mapping of the whole of Venus with a resolution of 15 to 30 meters (4 times greater than the images of the Magellan probe). The second will focus on nearly 30% of the surface to focus on the most geologically troubled regions (mountain, rift, etc.) but with better precision – 10 meters! If they believe in active tectonics, astrophysicists hope to better characterize the heat fluxes on the surface and, why not, observe the eruption of a volcano or see subduction zones. The third probe, Davinci + will focus on the atmosphere. Thanks to a mass spectrometer, it will analyze its composition in terms of gases which will make it possible to better understand the history of water and to know if it is a primitive atmosphere. “We will make discoveries that we did not even imagine”, predicts Thomas Widemann. See you after 2030.



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