Phosphine on Venus

Could a toxic gas be the key to discovering life on our neighboring planet?

Smelling of “garlic or decaying fish,” phosphine (PH₃) is listed as a lung-damaging agent by the Centers for Disease Control and Prevention (1). When inhaled, the gas can interfere with the body’s ability to produce proteins, cause severe damage to the nervous system, and even kill unsuspecting victims (1). Outside of Earth’s atmosphere, however, phosphine may signify the presence of organic material (2). Recently, scientists have discovered signs of the compound on Venus, which could bring the search for extraterrestrial life significantly closer to home.

Professor Jane Greaves of Cardiff University, along with a team of astronomers, detected the phosphine on Venus by using the James Clerk Maxwell Telescope in Hawaii (3). The radio telescope detects long radio waves over one millimeter in length (4). If phosphine was present, the researchers would pick up a specific discrepancy in the waves emitted by the planet (5). Using spectroscopy, they observed an absorption line indicating the wavelength at which an electron jumps to a higher energy state, which corresponded with phosphine’s absorption spectrum. The team confirmed their work by observing the planet with another radio telescope in the Atacama Desert. Since their discovery, Greaves’ group has published their findings in Nature magazine, demonstrating significant evidence to indicate that Venus’s atmosphere contains PH₃ (6).

News of the discovery has excited the scientific world because the quantity of phosphine discovered could indicate the presence of life on Venus. On Earth, small anaerobic microbes excrete phosphine from the synthesis of phosphate and hydrogen (7). Since Venus has an extremely different atmosphere from Earth, Greaves’ team considered whether the phosphine came from lightning or volcanic eruptions, which can also produce phosphine. Neither possibility, however, would create nearly enough of the compound; in fact, each would only produce one-thousandth of the phosphine observed (6). Although gaseous clouds cover much of the planet, some areas within its atmosphere may not be so highly pressurized or toxic (8). In theory, these more habitable environments could host organisms.

While promising, the presence of phosphine may not necessarily indicate life. Although scientists cannot currently explain the compound’s generation with any abiotic chemical processes, the source could be a new, undiscovered chemical process that does not necessarily occur on Earth (5). The team so far has found only one absorption line for the compound in their spectroscopic data, rather than multiple signs of phosphine’s presence (8). The only way to confirm the discovery is through more data, which will require further telescopic observation and potentially space exploration. Three space probes will pass by Venus in the next year, on voyages to Mercury and the Sun, so these crafts could theoretically bring equipment to monitor phosphine quantities (8). 

Whether by pointing to new forms of life or expanding scientists’ understanding of reactions in space, the discovery of phosphine on Venus may open new frontiers of science, in astronomy, chemistry and perhaps even biology.

– Julia Shephard

References

1. NIOSH. (N.D.). Phosphine: Lung Damaging Agent. CDC. Retrieved from https://www.cdc.gov/niosh/ershdb/emergencyresponsecard_29750035.html#:~:text=DESCRIPTION%3A%20Phosphine%20is%20used%20in,but%20is%20odorless%20when%20pure.
2. Byrne, P. (2020, September 18). The detection of phosphine in Venus’s clouds is a big deal – here’s how we can find out if it’s a sign of life. EarthSky. Retrieved from https://theconversation.com/the-detection-of-phosphine-in-venus-clouds-is-a-big-deal-heres-how-we-can-find-out-if-its-a-sign-of-life-146185
3. James Clerk Maxwell Telescope (2020, September 14). JCMT finds hint of life on Venus. East Asian Observatory. Retrieved from https://www.eaobservatory.org/jcmt/2020/09/jcmt-venus-news/
4. National Radio Astronomy Observatory (N.D.) What are Radio Telescopes? NRAO. Retrieved from https://public.nrao.edu/telescopes/radio-telescopes/
5. Zastrow, M (2020, September 17). Astronomers spy phosphine on Venus, a potential sign of life. Astronomy. Retrieved from https://astronomy.com/news/2020/09/astronomers-spy-phosphine-on-venus-a-potential-sign-of-life
6. Greaves, J and others (2020, September 14). Phosphine gas in the cloud decks of Venus. Nature. Retrieved from https://www.nature.com/articles/s41550-020-1174-4#Sec4
7. European Southern Observatory. (2020, September 20). What Is Phosphine and Why Does It Point to Extra-Terrestrial Life Floating in the Clouds of Venus? SciTechDaily. Retrieved from https://scitechdaily.com/what-is-phosphine-and-why-does-it-point-to-extra-terrestrial-life-floating-in-the-clouds-of-venus/
8. O’Callaghan, J. (2020, October 2). Life on Venus? Scientists Hunt for the Truth. Nature. Retrieved from https://www.nature.com/articles/d41586-020-02785-5
9. Stirone, S. Chang, C. Overbye, D. (2020, September 17). Life on Venus? Astronomers See a Signal in Its Clouds. New York Times. Retrieved from https://www.nytimes.com/2020/09/14/science/venus-life-clouds.html

Images

1. https://scx1.b-cdn.net/csz/news/800/2020/2-hintsoflifeo.jpg
2. https://www.eaobservatory.org/jcmt/wp-content/uploads/sites/2/2015/03/IMG_6436-1024×683.jpg