A new experiment unexpectedly shows that amino acids can survive in highly concentrated sulfuric acid, indicating that a form of life, different from carbon-based life forms on Earth, could potentially exist in Venus’ sulfuric clouds.
Venus’s surface is violently inhospitable, with temperatures reaching over 450 degrees Celsius (842F), widespread lava flows, and a suffocating atmosphere comprised of 96% carbon dioxide.
Scientists have speculated the possibility of life higher up in Venus’ clouds, where temperatures cool to match Earth’s surface, droplets in the clouds form a liquid environment, and the sun provides energy. In 2018, the detection of mysterious dark patches in the clouds caused excitement among scientists who compared the pattern to bacteria formations on Earth.
However, the presence of toxic sulfuric acid still poses a significant challenge to any possible microbial-type life forms in the clouds’ slightly more forgiving conditions.
Nevertheless, an unexpected discovery on the conditions on Venus occurred and was published on March 18th. A team from the Massachusetts Institute of Technology (MIT) released their study showing that amino acids, the fundamental building blocks of life, remain stable in highly concentrated sulfuric acid.
Sulfuric acid potentially replacing water for life
The team included Sara Seager, an astrophysicist and planetary scientist, her son, Maxwell Seager, an undergraduate at Worcester Polytechnic Institute, and William Bains, a research affiliate at MIT and scientist at Cardiff University.
The study consisted of 20 ‘biogenic’ amino acids, meaning that they are coded by Earth’s canonical genetic code, placed in sulfuric acid at concentrations of 81–98%, similar to Venus’ atmospheric conditions. Surprisingly, 19 of these chemicals, essential to life as we know it, remained stable with their molecular “backbone” still intact after 4 weeks.
Only one of these amino acids, tryptophan, became unstable. But as the researchers note, not all biochemicals remain stable in water either.
The results are promising; they indicate that a chemical as intensely corrosive as sulfuric acid could potentially be used as a substitute solvent for life in environments where water, essential for carbon-based life on Earth, is absent or unavailable.
The researchers explain that a small concentration of water vapor is present in Venus’s atmosphere, but the hydrogen molecules are locked in strong bonds to sulfuric acid, rendering the water unavailable. The lack of available water on Venus had previously washed out hopes for the possibility of life.
Professor Seager’s findings in previous experiments had already proved that fatty acids and nucleic acids remain stable in sulfuric acid, both complex organic molecules. This new experiment provides the missing piece in understanding Venus’s atmospheric conditions.
Maxwell Seager explains: “If you consider the four major building blocks of life as nucleic acid bases, amino acids, fatty acids, and carbohydrates, we have demonstrated that some fatty acids can form micelles and vesicles in sulfuric acid, and the nucleic acid bases are stable in sulfuric acid. Carbohydrates have been shown to be highly reactive in sulfuric acid,” he adds, “That only left us with amino acids as the last major building block to study.”
Possibility of non-carbon-based life forms?
So, if scientists continued to look exclusively for carbon-based life forms (the primary component of Earth’s life forms) in water-rich climates, their attention would remain on the more promising conditions of Mars, Jupiter’s moon Europa, and Saturn’s moons Titan and Enceladus.
But the results of this study reveal that a new perspective has emerged, focusing on the possibility of life forms different from those of Earth and therefore generating more attention to environments previously considered far too harsh to sustain life.
The results are significant because they “challenge the conventional planetary science view that only simple organic chemistry with limited functionality could be stable in sulfuric acid,” and although the survival of amino acids is not an indicator of life, life cannot exist without them. They link up to form protein chains necessary for many biological processes in organisms.
The possibility of life on Venus reached the headlines in 2020 following the detection of phosphine, a gas indicative of biological life. But this claim was later refuted when a study revealed that the data suggested the presence of sulfur dioxide, the third-most-common chemical compound in Venus’ atmosphere, and not a sign of life.
The results of MIT’s study also have important limitations — the experiment was conducted in a laboratory and used uncontaminated sulfuric acid, thus lacking other gases present in Venus’s atmosphere, such as carbon dioxide.
But although the findings of this study do not indicate life on Venus as we know it on Earth, they remain an important leap forward in understanding the conditions in the planet’s lower clouds.
The team responsible for this discovery is also spearheading a Venus Life Finder mission, slated for launch by the end of 2024. The spacecraft aims to detect signs of life in the Venusian atmosphere, potentially answering further questions raised by this study. But what has become clear is that the possibility of life on Venus should not be so readily dismissed.
