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- Venus, the world next-inward from Earth,<\/strong> is about the same size and density as Earth. But it\u2019s hot enough on its surface to melt lead.<\/li>\n
- Yet some studies have suggested oceans for Venus,<\/strong> billions of years ago, making it more Earth-like than it is today.<\/li>\n
- Now a new study suggests Venus never had oceans<\/strong>. Researchers studied Venus\u2019 atmospheric chemistry and concluded that there was never enough water in the planet\u2019s interior to support oceans on its surface.<\/li>\n<\/ul>\n
Did Venus ever have oceans? Was it ever habitable, even for some simple form of life, like microbes? Those are questions that scientists are still trying to answer. Some previous studies have suggested that the planet once was much more Earth-like, with lots of water on its surface. But now, a team of astronomers from the University of Cambridge in the U.K. are pointing to their new study, which disputes the idea of Venus oceans. They said on December 2, 2024, that their new work shows Venus likely never had enough water for oceans.<\/p>\n
The journal Nature Astronomy<\/em> published these researchers\u2019 peer-reviewed study on December 2, 2024.<\/p>\n
Looking for a great astronomy-themed holiday gift? The 2025 EarthSky lunar calendar is now available! A unique and beautiful poster-sized calendar. Keep up with all phases of the moon every night of the year.<\/p>\n
Temperate world or born hot?<\/h3>\n
Scientists have two main theories for what Venus was like billions of years ago. One says that the planet was similar to Earth, with abundant water on its surface. That theory supposes the water subsequently disappeared as Venus\u2019 atmosphere thickened, leading to the a runaway greenhouse effect \u2013 whereby a greenhouse gas like carbon dioxide blocks heat from leaving the planet\u2019s surface \u2013 seen today on Venus. Carbon dioxide buildup in the Venus atmosphere caused temperatures to soar, producing the hellishly hot world we see today.<\/p>\n
The other theory says that Venus \u2013 the 2nd world outward from the sun, closer to the sun than Earth \u2013 was born hot and has always been scorching. But which theory is more accurate?<\/p>\n
Studying Venus\u2019 atmospheric chemistry<\/h3>\n
To try to find the answer, the researchers looked at the current chemistry in Venus\u2019 atmosphere. Tereza Constantinou \u2013 lead author of the new study \u2013 is a PhD student at Cambridge\u2019s Institute of Astronomy. She said:<\/p>\n
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Both of those theories are based on climate models. But we wanted to take a different approach based on observations of Venus\u2019 current atmospheric chemistry. To keep the Venusian atmosphere stable, then any chemicals being removed from the atmosphere should also be getting restored to it, since the planet\u2019s interior and exterior are in constant chemical communication with one another.<\/p>\n<\/blockquote>\n
These scientists\u2019 statement explained:<\/p>\n
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Volcanism, through its supply of gases to the atmosphere, provides a window into the interior of rocky planets like Venus. As magma rises from the mantle to the surface, it releases gases from the deeper portions of the planet.<\/p>\n
On Earth, volcanic eruptions are mostly steam, due to our planet\u2019s water-rich interior. But, based on the composition of the volcanic gases necessary to sustain the Venusian atmosphere, the researchers found that volcanic gases on Venus are at most 6% water. These dry eruptions suggest that Venus\u2019s interior, the source of the magma that releases volcanic gases, is also dehydrated.<\/p>\n<\/blockquote>\n
![\"Gray](\"https:\/\/earthsky.org\/upl\/2024\/11\/Venus-Venera-13-March-1-1982.jpg\")
The Soviet probe Venera 13 captured this view of the Venusian surface after it landed on March 1, 1982. Venus\u2019 surface is scorching hot and barren. But did it once have water or was it always like this? Image via Wikimedia Commons\/ NASA (Public Domain).<\/figcaption><\/figure>\n Implications for life<\/h3>\n
If Venus was always dry, that fact would have implications for possible life. It would diminish the chances of life having started billions of years ago on the planet\u2019s surface, as well as the possibility that microbial life might exist now, as some have suggested, in Venus\u2019 clouds. The possibility of life in Venus\u2019 clouds has been a topic of much debate and controversy in recent years. Constantinou said:<\/p>\n
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We won\u2019t know for sure whether Venus can or did support life until we send probes at the end of this decade. But given it likely never had oceans, it is hard to imagine Venus ever having supported Earth-like life, which requires liquid water.<\/p>\n<\/blockquote>\n
Scientists supporting the idea of microbial life in Venus\u2019 clouds have suggested that it might have started when \u2013 or if \u2013 the planet first had water on its surface. Those organisms might later have retreated to the planet\u2019s atmosphere, when conditions on the surface became inhospitable. <\/p>\n
But even that scenario requires water on Venus\u2019 surface at some point. The key question is \u2026 was life ever<\/em> able to gain a foothold on Venus?<\/p>\n
Venus as an exoplanet analog<\/h3>\n
Knowing how Venus became the scorching world it is today will be a boon to those searching for possible life on distant exoplanets. As Constantinou noted:<\/p>\n
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Even though it\u2019s the closest planet to us, Venus is important for exoplanet science, because it gives us a unique opportunity to explore a planet that evolved very differently to ours, right at the edge of the habitable zone [the zone around a star in which liquid water might exist on a world\u2019s surface].<\/p>\n
If Venus was habitable in the past, it would mean other planets we have already found might also be habitable. Instruments like the James Webb Space Telescope (JWST) are best at studying the atmospheres of planets close to their host star, like Venus. <\/p>\n
But if Venus was never habitable, then it makes Venus-like planets elsewhere less likely candidates for habitable conditions or life.<\/p>\n
We would have loved to find that Venus was once a planet much more like our own, so it\u2019s kind of sad in a way to find out that it wasn\u2019t. But ultimately it\u2019s more useful to focus the search on planets that are mostly likely to be able to support life, at least life as we know it.<\/p>\n<\/blockquote>\n
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Venus Probably Never Had Oceans \u2013 It May Always Have Been Hell<\/p>\n
- Yet some studies have suggested oceans for Venus,<\/strong> billions of years ago, making it more Earth-like than it is today.<\/li>\n