Life on Venus

The possibility of life on Venus is a subject of interest in astrobiology due to Venus's proximity and similarities to Earth. Scientists have studied Venus using spacecraft and found that its current environment is very extreme compared to Earth’s. Despite these harsh conditions, researchers continue to explore whether life might have existed on Venus in the past before severe changes occurred, or whether some form of life could still survive in the planet’s upper atmosphere.

Venus has extremely high surface temperatures and pressure, making it difficult for water-based life like that on Earth to exist. However, some scientists think that special kinds of tiny organisms might be able to live in the cooler, acidic layers high above the planet’s surface. In 2020, researchers reported finding a gas called phosphine in Venus’s atmosphere, which could be a sign of life, although there is still uncertainty about these findings.

As of early 2021, scientists were still studying whether gases like phosphine or methane might indicate the presence of lifeforms on Venus or Mars. In June 2021, NASA planned two new missions called DAVINCI and VERITAS to learn more about Venus and its possibilities for supporting life.

Surface conditions

Main article: Observations and explorations of Venus

Venus is wrapped in thick clouds, so for a long time, people could only guess what its surface might be like. Long ago, many thought Venus might be similar to Earth and could maybe support life.

In 1962, the first spacecraft to visit Venus, called Mariner 2, measured the planet's temperature and found it to be very hot—about 500 degrees Celsius (900 degrees Fahrenheit). Since then, more visits by space probes showed that Venus has an extremely hot and heavy atmosphere. The heat comes from a strong greenhouse effect, and the air pressure on Venus is about 92 bars—nearly 100 times what we feel on Earth. With such a harsh environment, it is very unlikely that life as we know it could exist on Venus.

Past habitability potential

Scientists have wondered if Venus could have supported life in the past. Long ago, Venus might have had liquid water on its surface for up to 600 million years, which could have been enough time for simple life to form. Some studies even suggest Venus had water and conditions suitable for life for about 3 billion years, ending around 700 to 750 million years ago.

Because we have not studied Venus's surface much, finding evidence of past life might still be possible with special equipment. However, Venus's surface has changed dramatically in the last 500 million years, making it unlikely that ancient rocks with signs of life remain. Recent studies from October 2023 also suggest Venus may have had movements in its surface layers long ago, possibly creating more friendly conditions for life.

Main article: the process that delivered water to Earth

Main articles: Late Heavy Bombardment , tremolite , biosignatures , plate tectonics , habitable environment , life forms

Suggested panspermia events

Some scientists think life on Venus might have reached Earth carried on space rocks. This idea suggests that complex life could have developed on Venus and then arrived on Earth. However, this theory is not widely accepted and is considered unlikely.

Cataclysmic events

Around 700 to 750 million years ago, a major event changed Venus's surface and released gases that made its climate very hot. Some research also shows that if the planet Jupiter had not moved its orbit, Venus might have been able to support life.

Main article: lithopanspermia

Main articles: multicellular life , Cambrian , Ordovician , carbon dioxide , University of California, Riverside

Present habitability of its atmosphere

Although it is unlikely that life exists near the surface of Venus, some scientists think there might be possibilities a little higher up, about 50 kilometers above the surface where temperatures are milder. This idea started in 1950 by a German scientist named Heinz Haber. In 1967, Carl Sagan and Harold Morowitz wrote about this possibility in a science journal.

Scientists have found certain chemicals like carbonyl sulfide, hydrogen sulfide, and sulfur dioxide in Venus’s upper atmosphere. These chemicals were discovered during missions like Venera, Pioneer Venus, and Magellan. Some of these chemicals are hard to make without living things, but they can also come from volcanic activity. The sunlight can create sulfuric acid in the upper atmosphere from carbon dioxide, sulfur dioxide, and water vapor.

Some scientists think that if there are any tiny living things in Venus’s clouds, they might use the Sun’s ultraviolet light for energy. This idea came from Carl Sagan in 1963, who thought these tiny living things might be what causes some dark lines seen in pictures of Venus taken from space. In 2019, scientists noticed changes in Venus’s atmosphere that might be caused by unknown materials, perhaps tiny living things floating high up.

In 2020, some scientists thought they found a gas called phosphine in Venus’s atmosphere, which on Earth is sometimes made by living things. However, other scientists disagreed, and later studies suggested that the phosphine signal might have been wrong or very small. More observations are planned to learn more about these gases in Venus’s atmosphere.

Speculative biochemistry of Venusian life

Scientists have wondered how life might exist on Venus, even though its environment is very different from Earth's. In 2021, they found that the clouds on Venus have very little water, making it hard for life as we know it to survive there.

Later studies suggested that Venusian life might not use water but could be based on special molecules called "red oil." These molecules can exist in Venus's very acidic clouds. More recent research shows that some building blocks of life, like certain acids and amino acids, might also be stable in these conditions. These discoveries keep the question of life on Venus open for future exploration.

Speculative life cycles of Venusian life

Scientists in 2020 thought that tiny life on Venus might have a two-step life cycle. In one step, these tiny living things would stay busy inside cloud droplets to avoid drying out. When the droplets get heavy enough, they would fall into hotter parts of Venus and become small and light. Then, they might float back up to the cooler clouds by wind patterns, taking about a year.

Another idea from 2021 said this might not work because the lower clouds on Venus move very slowly. Instead, these tiny living things might change to soak up as much light as possible, making darker areas in the clouds. These darker spots might stay floating because the living things heat up the air around them. Or, they might stay up by a special effect caused by light.

Habitability of Venus for humans

The surface of Venus is not friendly for humans, but scientists have found that about 50 kilometers above the surface, conditions might be more comfortable. At this height, the air pressure, gravity, and temperature are similar to what we experience on Earth. Because of this, some people have suggested building floating habitats for humans to live in at these heights on Venus.