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A study led by astronomers at the University of Cambridge has determined that Venus has likely remained a dry, inhospitable planet for its entire history, countering long-standing speculation that the planet may have once hosted liquid water or conditions suitable for life.
Using an analysis of the chemical composition of Venus's atmosphere, the team inferred that the planet's interior lac 
by Sophie Jenkins
London, UK (SPX) Dec 03, 2024
A study led by astronomers at the University of Cambridge has determined that Venus has likely remained a dry, inhospitable planet for its entire history, countering long-standing speculation that the planet may have once hosted liquid water or conditions suitable for life.
Using an analysis of the chemical composition of Venus's atmosphere, the team inferred that the planet's interior lacks the moisture necessary to sustain oceans. This discovery challenges theories of a once temperate Venus and suggests its surface has always been unfit for Earth-like life.
The findings, published in Nature Astronomy, have significant implications for understanding Earth's unique habitability and refining the search for life on exoplanets. The study suggests astronomers should prioritize Earth-like planets over Venus-like ones in their search for habitable worlds.
"Venus and Earth may appear similar from a distance," said lead researcher Tereza Constantinou, a PhD candidate at Cambridge's Institute of Astronomy. "However, Venus's surface, with its intense heat and sulfuric acid clouds, tells a very different story. If Venus never had oceans, it's hard to imagine it ever supporting life like that on Earth."
Venus's Role in Understanding Habitability
Venus, Earth's closest planetary neighbor, has long been considered an important comparative tool for planetary science. Despite its extreme conditions, questions have persisted about whether it might have once harbored liquid water or currently supports aerial microbial life in its atmosphere."Venus provides a critical reference point for defining the habitable zone in planetary systems," Constantinou explained. "It's an invaluable example of how a rocky planet can evolve differently, even within a similar proximity to its star."
Two dominant theories have shaped debates about Venus's past. One posits that Venus was once temperate and water-rich but experienced a runaway greenhouse effect due to extensive volcanism. The other suggests Venus has always been too hot for water to condense, rendering it uninhabitable from its formation 4.6 billion years ago.
A New Approach
Instead of relying on climate models, the researchers focused on atmospheric chemistry. By calculating the destruction and replenishment rates of key molecules, including water vapor and carbon dioxide, the study examined the role of volcanic activity in maintaining the atmosphere's chemical balance.Volcanism, which releases gases into the atmosphere during eruptions, serves as a window into the planet's interior. On Earth, volcanic eruptions are steam-rich due to our water-abundant interior. On Venus, however, volcanic gases are only about six percent water, reflecting a dehydrated planetary interior.
"This data suggests Venus has been dry for most, if not all, of its existence," Constantinou noted. "The volcanic gases necessary to sustain the atmosphere don't indicate any significant water content in the interior."
Future Exploration
NASA's upcoming DAVINCI mission, set to launch by the end of the decade, will conduct flybys and deploy a probe to Venus's surface. These investigations aim to confirm the planet's historical dryness and further constrain theories about its evolution."If Venus has always been dry, it diminishes the chances of Venus-like exoplanets being habitable," Constantinou said. "We must focus our efforts on Earth-like planets, as instruments like the James Webb Space Telescope are optimized for studying planets closer to their stars, such as Venus."
While the findings may be disappointing for those hoping Venus once resembled Earth, they offer a clearer pathway for identifying habitable planets in the galaxy. "It's a bittersweet realization," Constantinou added. "But refining our understanding helps us better target our search for life elsewhere in the universe."
Research Report:A dry Venusian interior constrained by atmospheric chemistry
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Venus Express News and Venusian Science