Did Venus Have Oceans? This Surprising New Study Suggests Not, a Theory That Could Upend the Search for Extraterrestrial Life

As an Earth-sized rocky planet with a 1,000-degree-Fahrenheit surface temperature, Venus has long been dubbed our planet’s evil twin – a familial relationship emboldened by the common assumption that Venus may have once also been covered in oceans.

A team of astronomers at the University of Cambridge, however, has just posited that Venus may be less a twin than that thought in that it may never have even had oceans. Their findings, published Tuesday in the journal Nature Astronomy, could have important implications for Earthlings' search for extraterrestrial life.

“This doesn’t completely rule out any life. It rules out Earth-like life,” Tereza Constantinou, a Ph.D. student at Cambridge's Institute of Astronomy and first author of the study, tells the Guardian’s Nicola Davis.

Currently, Venus’ surface is the definition of inhospitable to life as we know it: the temperature is hot enough to melt lead, its air pressure is almost 100 times that of Earth and its toxic atmosphere hosts clouds of sulphuric acid. There are two leading theories on how Venus came to be the way it is: a wet version, and a dry version.

While both scenarios have a magma-sea beginning, the wet theory suggests that the planet eventually became temperate enough to host oceans of water, which ultimately disappeared when volcanic activity caused a runaway greenhouse effect. The dry theory, on the other hand, claims that Venus was born hot and remained so, never allowing water to collect on its surface.

Venus’s interior may have been dry for most of its history, challenging the hypothesis that the planet once hosted liquid surface oceans, according to a paper published in @NatureAstronomy: https://t.co/aqQXbanKJb

— Springer Nature (@SpringerNature) December 3, 2024

"Both of those theories are based on climate models, but we wanted to take a different approach based on observations of Venus' current atmospheric chemistry," Constantinou says in a statement.

The team studied Venus’ atmosphere to understand its interior. Our planetary neighbor’s atmosphere is unchanging, meaning the substances lost are constantly replenished by volcanic activity. By analyzing this replenishment, they could make assumptions about volcanic emissions, and thus about Venus’ interior.

Why is Venus’ interior important? Because in the wet scenario, the solidifying magma would have trapped water beneath its surface – water that Venus’ volcanoes should still be shooting into the atmosphere in significant quantities today

But they don’t. The team calculated that Venus’ eruptions are at most 6 percent water vapor. In contrast, Earth’s volcanic eruptions are over 60 percent water vapor.

"The atmospheric chemistry suggests that volcanic eruptions on Venus release very little water, implying that the planet's interior – the source of volcanism – is equally dry. This is consistent with Venus having had a long-lasting dry surface and never having been habitable," Constantinou tells Reuters’ Will Dunham.

However, Frank Mills, a planetary scientist at the Australian National University who was not involved in the study, is not convinced by its results. He tells Australia's ABC that though there isn’t a consensus about Venus’ oceanic history, most researchers support the wet scenario, and thus he needs more compelling evidence to be convinced otherwise.

In fact, Constantinou says that scientists won’t be able to fully resolve the wet-versus-hot debate until we send physical probes. Luckily, NASA’s DaVINCI mission is tentatively scheduled for 2030 and will study our evil twin with flybys and a probe, which scientists hope will survive the descent in extreme conditions for long enough to catch a quick look at the planet’s surface.

Venus Probably Never Had Oceans – It May Always Have Been Hellhttps://t.co/v5aTC3GH4m

— IFLScience (@IFLScience) December 2, 2024

In the meantime, the wet scenario has led scientists to use Venus (as well as Earth) as an example of what other potentially habitable worlds in the universe might resemble. Additionally, Venus is right on the edge of what astronomers call the “habitable zone,” the region around a star in which a planet’s temperature could allow for liquid water on its surface, and thus potentially host life. This means that the new study results don’t just challenge our understanding of Venus’ geological history, but partially upend how scientists have been searching for extraterrestrial life.

"If Venus was habitable in the past, it would mean other planets we have already found might also be habitable," Constantinou notes in the statement. "But if Venus was never habitable, then it makes Venus-like planets elsewhere less likely candidates for habitable conditions or life.”

She adds that they “would have loved to find that Venus was once a planet much closer to our own, so it's kind of sad in a way to find out that it wasn't.” Ultimately, however, the study will help focus the search for extraterrestrial life, “at least life as we know it,” she concludes.

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.