Author(s): Jacob Trusky
Mentor(s): Davis Kuykendall, Philosophy
Does life exist outside of Earth? If so, where is it found? Of all the candidates, Venus was ruled out due to its unsurvivable conditions. Venus has surface temperatures of about 700 K and an atmosphere that is 92 times denser than ours (Atmospheres 2020). However, the cloud layers at 50 km to 70 km above the surface have temperatures from 100 °C to −10 °C and atmospheric pressures from 1 atm to 0.1 atm (Venus 2020). Some scientists, such as Carl Sagan and Harold Morowitz, recognized these favorable conditions and proposed that life could exist in the clouds of Venus.
Sagan and Morowitz noted that the clouds of Venus contain all the parameters of life: “water, carbon dioxide, and sunlight” (Morowitz 1967: 1259). Additionally, the clouds of Venus absorb a lot of violet to ultraviolet light, and it is possible that phototrophic life in the clouds of Venus is causing this observation (Morowitz 1967: 1259). Recently, the presence of phosphine was detected in the clouds of Venus, which is a molecule that can only be produced naturally by life on Earth (Greaves 2020: 1). This project proposes to evaluate these findings and proposes an experiment that would help determine if life exists in the clouds of Venus.
Today we will be covering the mechanisms of survival for hypothetical Venusian life.
Now in order to address this question, we need to answer two questions.
First question is: Are the clouds of Venus hospitable? Life can survive in atmospheres. In fact, the only limiting factor is residence time and as it turns out, substances in the atmosphere of Venus stay there a lot longer than they do on Earth. The low pH of Venus’s clouds is not a limiting factor. We have found evidence of life that can thrive at ph 0. Water is available to life due to the hygroscopic nature of sulfuric acid. Basically, sulfuric acid acts like a sponge where it sucks in all the moisture from the atmosphere. Also, life could have adapted to the UV radiation. Venusian life could “deposit elemental sulfur on the outside of their cells to convert potentially harmful UV radiation” to usable light for photosynthesis.
Now the second question we have to ask is if the clouds of Venus actually have life. So phosphine has been detected in the clouds of Venus. Phosphine is a gas that can only be produced naturally by life on Earth. Also, there is an unknown absorber of 330 to 500 nanometers of light. It is possible that this unknown absorber is a photosynthetic organism. Also, “Venus did have a habitable climate for at least 750 million years,” with liquid water on its surface for as long as 2 billion years.
Now the two methods that my sources use:
The first one being spectroscopy. Spectroscopy studies the interaction between electromagnetic radiation and matter. In fact, each compound uniquely absorbs and emits different wavelengths of light, so the identity of a compound can be determined by analyzing the light it emits. This was used to determine that the absorber of 330 to 500 nanometers of light is still unknown. Because the wavelengths Venus’s clouds absorbs was compared to the wavelengths absorbed by every proposed absorber, and all these compounds were ruled out because they did not match. Also, this method was used to detect the presence of phosphine. The wavelengths phosphine emits aligned with the readings of Venus’s clouds.
Now the second method is: comparison to terrestrial life. We are looking for examples of life on Earth that can survive in Venusian conditions. This first organism, Acidithiobacillus ferrooxidans, is identified as the best terrestrial analogue because it grows in conditions like Venus’s clouds. It does this by coupling sulfur oxidation with ferric iron reduction under anaerobic conditions. Now another organism, green sulfur bacterium, also use sulfur-based metabolism under anaerobic conditions and it photosynthesizes using chlorosomes. Now chlorosomes are so important because they absorb between 330 and 500 nanometers of light. For this project, we will be focusing on the two chlorosome containing bacterium: the green sulfur bacterium Chlorobium tepidum and Chloroacidobacterium thermophilum.
Now I just want you to focus on the 350 to 500 range of light. Now I want you to notice that chlorosomes do absorb a lot of this light in between these two wavelengths.
So my final research question is: What are the mechanisms of sulfur and iron based metabolism and ultraviolet to violet light absorption that hypothetical Venusian life uses to survive? We’d be doing this by the creation of a genetically modified organism. We’d create a GMO of Acidithiobacillus ferrooxidans and one of the two chlorosome containing bacterium that I identified previously. Then we would simulate the conditions of Venus with bioreactors. This of course would be 96% carbon dioxide, 4% nitrogen gas, highly concentrated sulfuric acid, moderately high temperatures, and exposure to UV to violet light. Now the three requirements that need to be met for success of the experiment are the following. We need to create a GMO that can survive in Venusian conditions, use sulfur and iron based metabolism, and absorb violet to ultraviolet light for energy use. Now if such an organism is created it will be used to predict the characteristics of Venusian life. The mechanisms of metabolism and photosynthesis will be analyzed to predict the mechanisms of survival for the hypothetical Venusian organism.
Now here are my works cited and you can fact-check any of the stuff I provided. Thank you for watching this and I hope you have a great day.