Signs of Life on Venus?

Tia Tennariello ‘22

On September 14, 2020, the search for extraterrestrial life took an interesting turn when scientists discovered an earthly gas in the clouds of Venus. 

Phosphine is, on Earth, a noxious, flammable gaseous byproduct of anaerobic bacteria, or bacteria that do not require oxygen to survive. It is also present in the decomposition of organic matter.  However, the relationship between phosphine and terrestrial remains a mystery as researchers do not know what specific bacterium produces phosphine or why. Molecular astrophysicist and member of the discovery team, Clara Sousa-Silva explains, “We don’t know why life on Earth is making it, but it makes sense that only life is making it,” Sousa-Silva says. “Because spontaneously, it just wouldn’t be made in an  environment like Earth.” Ultimately, its association with natural processes however unclear they are, qualify phosphine as a biosignature, a possible sign of life.

This is an interesting discovery for scientists, who have been seeking to understand Venus for decades. It is second closest to the sun, but the hottest planet, melting all but its thick atmosphere of carbon dioxide and rolling clouds of sulfuric acid. Its temperature surpasses 800 degrees Fahrenheit while its pressure is more than 90 times that of Earth’s. These seemingly unbearable conditions beg the question, how did phosphine get to the Venusian atmosphere?

Because Venus’s scalding climate and acidic atmosphere would melt any rover, astronomers have turned to high-tech telescopes to study the planet from afar. In 2017, a study with James Clerk Maxwell Telescope in Hawaii, and in 2019 a study with the Atacama Large Millimeter/submillimeter Array compiled data on the gases scoped in Venus’s atmosphere. The

data discovered the phosphine’s spectral signature, the emittance of a substance with regard to its wavelength. At the time, they discovered about 20 parts-per-billion of phosphine in its sky. 

Scientists proposed alternative explanations for the presence of phosphine including lightning, volcanoes, meteorites or chemical reactions in clouds, but no definite conclusion was reached. Sara Seager, a coauthor on the subject and researcher at the Massachusetts Institute of Technology stated that “[One possibility] “is that some unknown chemistry is occurring in the Venus atmosphere, surface, or subsurface,”. “We find this explanation tough to accept because of Venus’s temperature and pressure range and the fact that Venus has nearly zero hydrogens mean(s) phosphine is not the natural form of the element phosphorus. Instead, phosphorus should be present as phosphates.” The source of the gas is unclear but may be clarified by more studies or samples in the future. 

While many aspects of the findings on Venus remain mysterious, they provide hope for “more research on Venus itself, research on the possibilities of life in Venus’ atmosphere, and even space missions focused to find signs of life or even life itself in the Venusian atmosphere,” Seager concluded in her interview. 

Current evidence may seem inexplicable or slight, but these steps are just the beginning. As research progresses, one cannot rule out the possibility of life past planet Earth.