Venus, often called Earth’s twin due to its similar size and mass, is a planet of extremes. Despite these similarities, Venus is a harsh environment with temperatures soaring above 400 degrees Celsius and atmospheric pressure over 90 times that of Earth. The thick atmosphere, primarily composed of carbon dioxide with clouds of sulfuric acid, creates conditions that are incredibly challenging for exploration.
Unlike Mars, which has been explored by numerous rovers, Venus has only been visited by stationary landers that survived for mere hours. The intense heat and pressure on Venus’s surface make it an unlikely candidate for life as we know it. However, some scientists have speculated that life might exist not on the surface, but within the planet’s dense clouds.
In 1967, Carl Sagan proposed that while Venus’s surface is inhospitable, its clouds might harbor life. Fast forward to today, and scientists have detected phosphine gas in Venus’s atmosphere, sparking excitement. Phosphine, a toxic and flammable gas, is typically associated with anaerobic bacteria on Earth. Its presence on Venus suggests either an unknown chemical process or potential microbial life.
Phosphine is considered a biosignature gas because it is usually produced by life forms in oxygen-free environments. On Earth, most life relies on oxygen, but phosphine’s presence indicates that life could exist in non-Earth-like conditions. The gas is difficult to produce without biological processes, requiring high temperatures and abundant hydrogen, conditions not typically found on rocky planets like Venus.
When researchers observed Venus using the Atacama Large Millimeter/submillimeter Array (ALMA), they found phosphine levels far exceeding those on Earth. This discovery suggests something unusual is happening on Venus. One theory is that phosphine could be a remnant of a past biosphere, with microbes adapting to survive in the clouds after Venus’s climate drastically changed.
While the idea of life in Venus’s clouds is intriguing, the extreme acidity poses a significant challenge. Earth’s most resilient extremophiles can only withstand about 5% acidity, whereas Venus’s clouds are over 90% acidic. This makes it unlikely that Earth-origin microbes could survive there.
Before concluding that phosphine indicates life, scientists must eliminate other potential sources. They considered chemical reactions from lightning, volcanic activity, and meteorite impacts, but none could account for the detected phosphine levels. Despite the presence of volcanoes on Venus, they appear inactive, and meteorite contributions are negligible.
While the phosphine detection is not definitive proof of life, it highlights unexplained chemistry on Venus. Some scientists question the detection due to the faint signal, but repeated observations have confirmed the findings. If further research supports the phosphine presence, the next step would be sending a spacecraft to Venus to gather more data.
The possibility of life on Venus has reignited interest in space exploration. For those curious about the cosmos, platforms like CuriosityStream offer documentaries that delve into space exploration and other scientific topics. Their partnership with Nebula provides access to unique educational content, supporting creators and expanding our understanding of the universe.
As we continue to explore the mysteries of space, Venus stands out as a fascinating subject, reminding us of the vast possibilities that await discovery beyond our planet.
Engage in a lively debate with your classmates about the implications of phosphine detection on Venus. Split into two groups: one supporting the hypothesis of microbial life and the other arguing for non-biological explanations. Prepare your arguments using scientific evidence and present them to the class.
Conduct a lab experiment to simulate the conditions of Venus’s clouds. Use materials to create a model atmosphere and test how different substances react under high acidity and pressure. Document your findings and discuss how these conditions might affect potential life forms.
Draft a research proposal for a hypothetical mission to Venus. Outline the objectives, instruments, and methods you would use to investigate the presence of phosphine and potential life. Present your proposal to peers for feedback and refine it based on their suggestions.
Watch a documentary on Venus exploration, such as those available on CuriosityStream. After viewing, participate in a group discussion to analyze the content, focusing on the challenges and breakthroughs in studying Venus. Reflect on how this knowledge impacts our understanding of life in the universe.
Write a short story or essay imagining life in the clouds of Venus. Consider the adaptations necessary for survival in such extreme conditions. Share your creative work with classmates and explore the scientific plausibility of your ideas through peer review.
This episode of Real Science is brought to you by CuriosityStream. Watch dozens of space documentaries and get free access to Nebula for just $14.79 a year by signing up at curiositystream.com.
Real Science: Venus, the second planet from the sun, is sometimes referred to as Earth’s twin. Nearly the same size with about the same mass, both planets have significant atmospheres. However, in spite of their similarities, Venus is a toxic hellscape compared to Earth. Temperatures can reach more than 400 degrees Celsius, and the pressure is staggering—more than 90 times higher than on Earth. Standing on the surface of Venus would be like standing 900 meters below the ocean surface in terms of pressure. This extreme pressure and heat are due to its thick atmosphere, composed mainly of carbon dioxide, with clouds made of sulfuric acid. The crushing pressure and immense heat make Venus a particularly challenging place to explore.
While we have heard many stories about Mars rovers, we’ve never heard about a Venus rover because there has never been one. The longest mission to the surface of Venus was a stationary lander that survived for only two hours. It’s so hot on the surface that metals like lead would completely melt, and the pressure is so high it could crush a nuclear submarine. Consequently, the idea of any life existing there has always seemed far-fetched. Most scientists have focused their search for extraterrestrial life on planets like Mars or moons such as Europa and Enceladus. However, some experts have suggested that life may indeed be possible on Venus—not on its sweltering surface, but within its thick clouds.
In 1967, Carl Sagan wrote that while the surface conditions of Venus make the hypothesis of life there implausible, the clouds of Venus are a different story altogether. Now, 53 years later, scientists may have found the first sign of this hypothesis being true: phosphine gas detected in extremely high levels in the atmosphere of Venus. Phosphine gas may not sound significant to most, but it has scientists around the world excited.
Phosphine is a colorless, flammable, and toxic gas with the chemical formula PH3. It was used as a chemical weapon during World War I and is currently used as an agricultural fumigant. It is also a byproduct of certain anaerobic bacteria—organisms that live in environments without oxygen, such as marshes and landfills. Unless humans have manufactured the phosphine, the only known way it can be produced on rocky planets like ours is through these microbes. For this reason, scientists have determined it to be an appropriate biosignature gas, which is a gas produced by life that accumulates in an atmosphere to detectable levels.
On Earth, the majority of life is centered around oxygen, a byproduct of photosynthesis. Methane and nitrous oxide are also among Earth’s biosignature gases, but scientists recognize that focusing solely on these gases would be a very Earth-centric approach. Life could exist in non-Earth-like environments, such as places without oxygen. Just like in anaerobic environments on Earth, a planet without oxygen could still produce phosphine as a sign of life.
Phosphine is particularly compelling as a biosignature because it does not form easily. It requires specific thermodynamic conditions to be produced outside of biological life, needing extremely high temperatures and plenty of elemental hydrogen. Scientists do not know of any way phosphine can be produced on a planet with temperatures below 527 degrees Celsius. For example, the gas giant Jupiter has high levels of phosphine gas, forming in the hottest, deepest layers of its atmosphere where hydrogen is abundant. However, on rocky planets like Earth and Venus, lower temperatures, pressures, and hydrogen quantities make phosphine gas almost impossible to find.
When researchers pointed their telescopes at Venus, they were astonished by what they observed. The Atacama Large Millimeter/submillimeter Array (ALMA) detected far more phosphine than exists on Earth—20 parts per billion compared to Earth’s 7 parts per trillion. If phosphine is indeed in the atmosphere of Venus, it indicates something extraordinary is happening—either something is creating phosphine in an unexpected chemical event, or alien life is producing it as a byproduct, similar to anaerobic bacteria on Earth.
One theory suggests that if the phosphine detected in Venus’s atmosphere is a sign of life, it could be a relic of a previous biosphere—an ancient remnant of a once-thriving ecosystem that eventually collapsed due to the runaway greenhouse effect that created present conditions. If life formed in the past, it might have adapted to survive in the clouds when intense climate change boiled the oceans away, killing the rest of the biosphere. Microbes in the clouds may have become the last survivors on Venus.
While the idea of life existing suspended in clouds may seem strange, it is not entirely alien to life on Earth. In 2005, researchers collected samples from different levels of Earth’s stratosphere and detected various bacterial and fungal colonies. Since then, microbes from every major biological lineage have been found in Earth’s upper atmosphere. This strange behavior of microbes could also be plausible on Venus.
However, the extremely acidic conditions in Venus’s clouds pose a significant challenge for life as we know it. Even the most durable extremophiles on Earth can withstand only around 5% acidity, while the conditions in Venus’s clouds are over 90% acidic. This is also why we can rule out the idea that any of our Venus probes accidentally dropped off microbes; anything from Earth could not survive there.
Before we can get too excited about the possibility of phosphine indicating alien life, scientists need to rule out any other potential chemical reactions on Venus that could lead to phosphine production. Researchers examined other possible origins of the gas, such as chemical reactions driven by lightning, volcanic activity, or delivery by meteorites. They noted that while lightning can occur on Venus, it happens much less frequently than on Earth and would not produce enough energy to create phosphine. They estimated that there would need to be more than 200 times as much volcanic activity on Venus as on Earth to inject enough phosphine into the atmosphere to be detectable. While there are thousands of volcanoes on Venus, none appear to be active.
Even if every single volcano on Venus were active, researchers believe that the maximum production of phosphine by volcanoes would still be significantly lower than the levels required for detection. Assuming Venus receives the same amount of meteorites as Earth each year, the contribution of phosphine from these meteorites would be negligible.
Scientists simply do not know of any way phosphine can be produced on a planet with Venus’s temperatures and pressures and limited hydrogen. However, this does not mean it is impossible. The authors of the study emphasize that the detection of phosphine is not robust evidence for life, but rather for anomalous and unexplained chemistry. Some scientists even doubt the phosphine detection itself, as the signal was faint and required extensive processing to extract from the data. However, researchers have repeated their findings with two different telescope arrays and found similar patterns of detection.
There is certainly enough here to be excited about, but perhaps not about alien life just yet. If researchers can confirm the phosphine detection beyond doubt and continue to find it unexplained, the next step will be sending a spacecraft to Venus to investigate further, collecting samples of the gas or even potential alien life.
As Carl Sagan once said, extraordinary claims require extraordinary evidence. As the planetary science community sets its priorities for the next decade of space exploration, Venus has moved to the forefront of the list.
If you’re like me, all this talk about space and the possibility of life on other planets has reignited a curiosity that may have dwindled over time. It’s something we grow up excited about, but life often gets in the way. It’s been a while since I’ve laid in the grass and looked up at the stars, letting the incredible vastness of it all sink in. Since learning about the phosphine discovery on Venus, I feel compelled to escape the city lights and do just that.
Exploring space and understanding recent discoveries can help reignite the curiosity within us. If you need a break from reality, want to ponder the universe’s vastness, or reignite a lost interest in the cosmos, check out the space exploration documentaries on CuriosityStream. The eight-part series “The Planets,” made by the BBC, is particularly worth watching. The episode titled “Giants” explains a significant discovery that made the dream of flying to the giant planets a reality and showcases how scientists navigated what seemed impossible—sending the Voyager probe billions of miles from Earth to explore the outer planets of our solar system.
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Venus – The second planet from the Sun, known for its thick, toxic atmosphere and surface temperatures high enough to melt lead. – Scientists are intrigued by Venus because its harsh conditions provide a stark contrast to Earth, offering insights into planetary evolution and climate change.
Phosphine – A colorless, flammable, and toxic gas that has been detected in the atmosphere of Venus, sparking interest due to its potential biological origins. – The discovery of phosphine in the clouds of Venus has led researchers to speculate about the possibility of microbial life existing in its atmosphere.
Life – A characteristic that distinguishes physical entities with biological processes, such as signaling and self-sustaining processes, from those that do not. – The search for extraterrestrial life often focuses on finding environments where water and organic molecules can support biological activity.
Atmosphere – The layer of gases surrounding a planet, which can influence its climate and potential to support life. – The thick atmosphere of Venus is composed mainly of carbon dioxide, with clouds of sulfuric acid, making it a challenging environment for exploration.
Exploration – The systematic investigation of celestial bodies to gather data and expand our understanding of the universe. – Space agencies around the world are planning missions for the exploration of Venus to better understand its geology and atmospheric conditions.
Biosignature – A substance or phenomenon that provides scientific evidence of past or present life. – The detection of certain gases, like methane or phosphine, in a planet’s atmosphere can serve as a potential biosignature, indicating biological processes.
Acidity – The level of acid in substances, which can affect chemical reactions and the potential for life in different environments. – The high acidity of Venus’s clouds poses a significant challenge for the survival of any potential life forms.
Microbes – Microscopic organisms, which can include bacteria, archaea, and some fungi, that can survive in extreme environments. – The possibility of microbes existing in the upper atmosphere of Venus is an exciting prospect for astrobiologists studying life’s adaptability.
Chemistry – The branch of science concerned with the properties, composition, and behavior of elements and compounds. – Understanding the chemistry of Venus’s atmosphere is crucial for interpreting the potential signs of life and the planet’s climatic history.
Clouds – Visible masses of liquid droplets or frozen crystals suspended in a planet’s atmosphere, which can play a role in climate and weather patterns. – The clouds of Venus are composed of sulfuric acid, creating a highly reflective layer that obscures the planet’s surface from view.
