Science & Technology

New discoveries suggest that Venus did not have a sea, a necessary condition for life

This image of the night side of Venus shining with thermal infrared rays was taken by the Japanese Akatsuki spacecraft. Credits: JAXA / ISAS / DARTS / Damia Bouic

Astrophysicists led by UNIGE and NCCR Planet S Venus To find out if Earth’s sister planet once had an ocean.

The planet Venus can be seen as the evil twins of Earth. At first glance, it has the same mass and size as our home planet, as well as mostly composed of rocks, holding some water and having an atmosphere. Still, a closer look reveals the striking differences between Venus’s thick CO2 atmosphere, extreme surface temperatures and pressures, and sulfuric acid. acid Clouds are certainly in stark contrast to the conditions necessary for life on Earth. However, this is not always the case.

Previous studies have suggested that Venus may have been a much kinder place in the past, in its own sea of ​​liquid water. A team of astrophysicists, led by the University of Geneva (UNIGE) and the Swiss National Center for Research Ability (NCCR) PlanetS, investigated whether the twins of our planet actually had a calm period.Results published in the journal Nature, It is recommended that this is not the case.

Early Venus surface and atmosphere

The artist’s view of the surface and atmosphere of early Venus over 4 billion years ago. In the foreground is a mysterious explorer who was surprised to see the ocean completely evaporate in the sky.Credit: © Manchuria

Venus has recently become an important research topic for astrophysicists. With ESA NASA This year, we have decided to send more than three space missions to the planet closest to the Sun over the next decade. One of the key questions these missions are trying to answer is whether Venus has hosted the early oceans. An astrophysicist led by Martin Turbet, a researcher at UNIGE’s Faculty of Science and Astrophysicist and a member of NCCR Planet S, sought to answer this question using tools available on Earth.

“We simulated the climate of Earth and Venus in the first stages of evolution, more than 4 billion years ago, when the planet’s surface was still melting,” explains Martin Turbet. “The associated high temperature meant that every water was present in the form of steam, like a giant pressure cooker.”

The team uses a sophisticated three-dimensional model of the atmosphere, similar to what scientists use to simulate the Earth’s current climate and future evolution, and which of the two planets’ atmospheres over time. I studied how it evolves and whether the ocean is formed in the process.

“Thanks to our simulations, we were able to show that climatic conditions were unable to condense water vapor in Venus’ atmosphere,” says Martin Turbet. This means that the temperature will never drop enough for water in the atmosphere to form raindrops that can fall on its surface. Instead, water remained in the atmosphere as a gas, and the sea was never formed. “One of the main reasons for this is the clouds that preferentially form on the night side of the planet. These clouds cause a very strong greenhouse effect, causing Venus to cool as quickly as previously thought. “I hindered that,” continued Geneva researchers.

Small differences with serious consequences

Surprisingly, astrophysicist simulations also reveal that Earth could have easily suffered the same fate as Venus. If the Earth were a little closer to the Sun, or if the Sun was shining as bright as it is today at its “youth,” our home planet would look very different today. It may be the relatively weak radiation of the young sun that was able to cool the Earth enough to condense the water that forms our ocean. Emeline Bolmont, a professor at the University of Geneva, a member of PlanesS, and co-author of the study, said: It has always been regarded as a major obstacle to the emergence of life on Earth! The argument was that if the sun’s radiation were much weaker than it is today, it would have transformed the Earth into a sphere of ice that is hostile to life. “But for a young and very hot planet, this weak sun may have been an unexpected opportunity,” the researchers continue.

“Our results are based on theoretical models and are an important component in answering questions about the history of Venus,” said research co-author David Ehrenreich, a professor of astronomy at UNIGE and a member of NCCR Planet S. Stated. “But our computer cannot clearly determine this issue. Observations of the three future Venus space missions are essential to confirm or refute our work.” “These fascinating questions can be addressed by the new Space Life Center just set up within UNIGE’s Faculty of Science,” pleases Emeline Bolmont.

See: “Day and night cloud asymmetry prevents the early oceans on Venus, but on Earth,” Martin Turbet, Emerine Bolmont, Guillaume Chaverot, David Ehrenreich, Jérémy Leconte, Emmanuel Marcq, October 13, 2021. Nature..
DOI: 10.1038 / s41586-021-03873-w

New discoveries suggest that Venus did not have a sea, a necessary condition for life New discoveries suggest that Venus did not have a sea, a necessary condition for life

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