A team of astronomers has determined that life never existed on Venus, challenging decades-old theories that suggested our closest planetary neighbor may once have been more Earth-like than it is today.

Researchers from the University of Cambridge examined the chemical composition of Venus’ atmosphere and concluded that the planet’s interior is now too arid to contain enough water for surface oceans. So Venus likely remained an extremely hot and inhospitable world throughout its existence.

These findings were published in the journal Nature AstronomyIt has a significant impact on understanding the uniqueness of the Earth and the ongoing search for extraterrestrial life. Although many exoplanets exhibit Venus-like properties, the study advises astronomers to opt for exoplanets that are more Earth-like in nature.

Venus’ hostile environment

From afar, Venus and Earth look similar: Venus is nearly the same size and, like Earth, is a rocky planet. But on closer inspection, Venus resembles an “evil twin” with thick clouds of sulfuric acid and an average surface temperature of around 500°C. Despite these harsh conditions, astronomers have long wondered whether Venus once had liquid oceans that could support life, or whether some form of “aerial” life exists in its dense clouds today.

“We won’t know for sure whether Venus can support life until we send probes later this decade,” said first author Teresa Constantinou, a postdoctoral researcher at the Institute of Astronomy in Cambridge.

“But given that Venus likely never had oceans, it is difficult to imagine Venus supporting Earth-like life that would require liquid water.”

Landmark for residential area

In the search for life beyond our galaxy, astronomers are targeting planets within the habitable zones of their stars, where conditions allow liquid water on the surface. Venus serves as a critical landmark for determining the boundaries of this habitable zone.

“Although Venus is the closest planet to us, it is important for exoplanet science because it gives us a unique opportunity to study a planet that has evolved very differently from ours, located right at the edge of the habitable zone,” Constantinou said. he said.

Two rival theories about Venus’ past

There are two main hypotheses regarding the evolution of Venus since its formation 4.6 billion years ago. The first suggests that the surface of Venus once had temperate conditions containing liquid water, but that the greenhouse effect caused by intense volcanic activity caused the planet to warm. The second hypothesis suggests that Venus was born hot and could never host liquid water on its surface.

“Both of these theories are based on climate models, but we wanted to take a different approach based on observations of the current chemistry of the Venus atmosphere,” Constantinou said. “To keep Venus’s atmosphere stable, any chemicals removed from the atmosphere must also be returned to it, as the interior and exterior of the planet are in constant chemical contact with each other.”

Volcanic evidence and dehydration

Researchers calculated the rate at which water, carbon dioxide and carbonyl sulfide molecules break down in Venus’ atmosphere. These molecules must be replenished by volcanic emissions to keep the atmosphere stable. Volcanic activity, which releases gas into the atmosphere, helps us understand the interior of rocky planets like Venus. As magma rises from the mantle to the surface, it releases gases from the planet’s deeper layers.

Volcanic eruptions on Earth mostly release steam because our planet is rich in water. But based on the composition of volcanic gases necessary to maintain Venus’ atmosphere, researchers determined that volcanic emissions on Venus contain no more than six percent water. These dry eruptions suggest that the interior of Venus, which supplies the magma that releases volcanic gases, also lacks significant amounts of water.

Improving the search for life-supporting planets

By the end of this decade, NASA’s DAVINCI mission will be able to test and verify with a series of flybys and a surface probe whether Venus was always a dry, inhospitable planet. The mission’s results could help astronomers improve their search for life-supporting planets around other stars in the galaxy.

“If Venus had been habitable in the past, this would mean that other planets we have already found might also have been habitable,” Constantinou said. he said.

“Instruments such as the James Webb Space Telescope are best suited to study the atmospheres of planets close to their stars, such as Venus. But if Venus was never habitable, this makes Venus-like planets elsewhere less likely candidates for habitable conditions or life.”

“We’d like to find out that Venus was once a planet much closer to our planet, so it’s a bit sad to find out it wasn’t, but ultimately it’s more beneficial to focus our search on planets that might have been much closer to this planet.” to support life – at least life as we know it.” “.