Life on Venus: The Potential Habitability of Venusian Clouds

Ever since humans began exploring space, we looked for life or possible habitability outside of our planet. Our space agencies have studied nearby planets like Mars, and considered future probes of ocean worlds like Jupiter’s moon Europa, always in search of the possibility of even further distant planets that could more closely resemble our own.

But what if the existence of life was possible on the hottest planet in our solar system? Despite being a hellish volcanic planet, Venus might not be completely inhospitable, according to a group of researchers who have reported a chemical model of the Venusian atmosphere that suggests some specific forms of life could potentially live in our neighbor planet’s clouds.


Background: Taking a look at the Morning Star

Venus is not the planet closest to the sun, but its atmosphere is so dense that it can trap huge amounts of heat, increasing the temperature of the planet to a point where it can melt lead (and then some). 

Several space programs sent missions to remotely probe Venus in the past, although they produced little information as they were completely melted by the extreme temperatures of the planet, or crushed by the pressure of its atmosphere. The Venera probes, by the Soviet Union, were the first to successfully capture and transmit any information from this planet back to Earth.

Last year, researcher Sara Seager and her team published a paper in which they reported the discovery of a potential biosignature gas for exoplanets–a possible sign of life–in Venus’ atmosphere. Through powerful telescopes, Seager’s team detected phosphine, a chemical that (as far as science knows) can only be produced by living beings on rocky planets such as Earth and Venus.

“There is a chance we have detected some kind of living organism in the clouds of Venus,” Cardiff University astronomer Jane Greaves, who led the United Kingdom-based team, said during their announcement of the discovery. “This is very exciting and was really very unexpected.”

This discovery was indeed met with a lot of excitement but it also brought up some questions as well. Other researchers wondered if the chemical could’ve resulted from unknown and unexplained atmospheric or geological processes. In fact, subsequent studies actually refuted the phosphine findings.


Image: NASA/JPL-Caltech, Peter Rubin

“Instead of phosphine in the clouds of Venus, the data are consistent with an alternative hypothesis: They were detecting sulfur dioxide,” said co-author Victoria Meadows, a UW professor of astronomy. “Sulfur dioxide is the third-most-common chemical compound in Venus’ atmosphere, and it is not considered a sign of life.”

This didn’t discourage researchers from continuing to focus their attention on our neighboring planet. Even though the surface of Venus is, in fact, inhospitable there’s a particular cloud layer in the atmosphere, about 30 miles below the top, which reaches lower temperatures (86 degrees Fahrenheit) and has a similar pressure to the one of Earth’s ground.


Analysis: Sugar, spice, and a little bit of ammonia

In a new study, Seager and her colleagues managed to model the chemistry of Venus’ atmosphere and created a hypothesis that involves the presence of ammonia, a chemical that has been previously detected in Venus, by probes. The model explains that ammonia could potentially interact with the abundant sulfuric acid droplets in the clouds, neutralizing their acidity and forming ammonium sulfite salts.

Venus’s atmosphere still displays many characteristics that we’re unable to explain, like small amounts of oxygen and particles of unknown composition. When questioned about these particles, Seager answered that “most of the particles in the atmosphere are concentrated sulfuric acid droplets. They are there because of chemical formation processes.”

“Some of the particles – Mode 3 – have an unknown composition. In the paper we explain our theory that some of the Mode 3 particles may have ammonia in them, creating a kind of ammonia salt slurry.” –  Seager told The Debrief. These semisolid ammonium salt slurries would still be highly acidic but able to be neutralized within the pH range of some extreme Earth environments in which some microbes – extremophiles – can still live in.

These findings suggest that there might be potentially habitable conditions in the atmosphere of Venus, specifically that microbial-type life might reside inside the neutralized droplets in the clouds.

The source of ammonia on Venus is unknown. In the paper, the authors assume that there’s a possibility that it might result from biological processes, which could also maybe explain the presence of small amounts of oxygen.


Outlook: Finding life in unexpected places

On the Venus Cloud Life website, run by Sara Seager and two other colleagues, one can learn more about their studies regarding the importance of studying Venus and its atmosphere. 

The conditions on the “hospitable” Venusian cloud layer are drier than the driest place on Earth and way more acidic than the most acidic environment we have on our planet, so it’s safe to say that whatever microbial life that might exist there would be a lot different than the extremophiles from Earth.

Image Credit: Pixabay

Seager is leading a Venus life finder mission concept study that aims to search for signs of life or microbial-type life detection by sending a series of repeat missions to our scorching neighbor. “A major motivation are unexplained atmospheric chemical anomalies, including the ‘mysterious UV-absorber’, tens of ppm O2, SO2 and H2O vertical abundance profiles, the possible presence of PH3 and NH3, and the unknown composition of Mode 3 cloud particles.” – the website reads.

The Debrief questioned Seager about the impact that finding microbial life in Venus would have in the future of space studies and explorations. She believes that if life exists in Venus, then the possibility of life in other places is endless.

“Future in-situ space probes are needed to search for actual life forms,” Seager told The Debrief. “If we find microbial life anywhere beyond Earth it means there is the possibility for life in so many places.” 

Raquel is a forensic geneticist turned freelance writer. She has a knack for technology and a passion for science. You can follow her at and on Twitter @theRaquelSantos.