Scientists may be getting warmer in the search for life in the cosmos. Research released on September 14, 2020 in the journal of Nature Astronomy suggests the discovery of phosphine gas in the atmosphere of Venus – a possible signature of microbial life on our planetary neighbor.

While an exciting discovery, much is still unknown about Venus and further research is necessary to determine the true cause of these phosphine gas concentrations.

Venus Overview

Venus as viewed by NASA’s Mariner 10 probe on February 7, 1974. These images were newly-processed and released by NASA in 2020. Credit: NASA/JPL-Caltech

Venus is often considered a hellish world, inhospitable to life as we know it on Earth. Due in part to a runaway greenhouse effect, the Venetian surface experiences temperatures approaching 900 degrees Fahrenheit with crushing pressures nearly 90 times that on the surface of Earth. The planet’s thick atmosphere is made primarily of carbon dioxide with clouds that rain sulfuric acid.

While being the planet that gets closest to Earth in our orbits, Venus has proved difficult to explore due to the the intense heat and pressure. Spacecraft, like the Soviet Union’s Venera 13 mission, have only survived on the surface for mere minutes before succumbing to the harsh environment.

The surface of Venus appears to be a volcanic wasteland, but approximately 30-40 miles up in the atmosphere temperatures and pressures become similar to that on Earth. Here, high in the cloud decks, is where scientists hold out hope for some form of microbial life.

What did we find?

Chemical structure of phosphine (PH3).

New research discovered concentrations of phosphine gas high in the atmosphere of Venus. Phosphine is considered a biosignature – a chemical thought to be produced primarily through life processes. Scientists use biosignatures to search for signs of life on other planets.

On Earth, phosphine gas is produced by bacteria in environments lacking oxygen. Phosphine is found in swamps, the intestines, and other low-oxygen areas where bacteria flourish.

While living organisms are one producer of phosphine, this chemical can also be produced through other methods. Volcanic activity is another producer of phosphine on Earth, and the chemical has been found in the atmospheres of Jupiter and Saturn due to known chemical processes deep within the Gas Giant planets’ cores.

Currently understood processes on Venus cannot explain the concentrations of phosphine gas present in the planet’s atmosphere. The presence of life is only one possible explanation.

How did we find it?

Spectra showing the detection of phosphine in Venus’s atmosphere as seen by the JCMT observatory (left) and the ALMA observatory (right). Credit: Greaves et. al. 2020

Scientists look for biosignatures in a planet’s atmosphere using spectroscopy. By studying the light that passes through a planet’s atmosphere, scientists can determine the chemicals surrounding the planet.

The research team used observations from the James Clerk Maxwell Telescope (JCMT) in Hawaii and the Atacama Large Millimeter Array (ALMA) in Chile to confirm the spectra pattern corresponding to phosphine. The above graphs can be thought of as a “fingerprint” suggesting the presence of phosphine gas in the Venetian atmosphere.

Spectroscopy is also used to search for biosignatures around exoplanets – planets outside of our solar system. However, exoplanets are so distant that we do not have the technology to physically visit them. The discovery of a possible biosignature around Venus is exciting because the planet is close enough to Earth to send a future mission for more detailed exploration.

What does it mean?

Venus is currently visible in the morning sky over St. Louis. Credit: EG, Stellarium

This research does not yet confirm the existence of life on Venus, but it is an exciting discovery.

Scientists will want to independently confirm these new findings to ensure the data is accurate and free from misinterpretation. Even if the research is confirmed, we can not currently rule out unknown processes that could create the phosphine found in the atmosphere of Venus. Life is only one possibility.

Science changes daily. Our understanding of Venus, and life itself, is still at a very primitive stage. The question of microbial life in the atmosphere of Venus is just the most recent way of asking if we are alone in the universe. It is this question, and all the unknowns that surround us, that have fascinated humans since we first gazed upon the starry sky.

While we continue to ponder these questions, Venus is currently visible in the morning sky over St. Louis. For current viewing tips, visit our weekly Night Sky Update.