Gas on Venus Hints at Extraterrestrial Life

For decades, scientists have hypothesized about the existence of extraterrestrial life. This curiosity has escaped labs and traveled into pop culture, as seen in movies such as “E.T. the Extra-Terrestrial” (1982) or the cultural obsession over Area 51. As of September, scientists may be one step closer to discovering it. Researchers from the Massachusetts Institute of Technology (MIT) and the University of Cambridge published research on September 14, 2020, that there could be life on Venus.

Though scientists have considered life on other planets such as Mars and an Earth-like planet 400 light-years away called Kepler 78b, few have considered life on Venus due to its inhospitable conditions. Its thick atmosphere reaches scorching temperatures, and poisonous clouds of sulfuric acid surround the planet. Despite often being called Earth’s “evil twin,” Venus has a cloud layer 31 miles into its atmosphere that may be hospitable. The Atacama Large Millimeter/submillimeter Array (ALMA), the largest radio telescope in the world, detected high concentrations of phosphine in this layer. Phosphine, a chemical made up of phosphorus and hydrogen, is commonly associated with life because it can be generated by decaying organic matter and anaerobic organisms.

Phosphine isn’t unique to Earth or Venus; it is also present on planets such as Jupiter and Saturn. What makes the discovery of phosphine on Venus special is that, unlike Earth and Venus, Jupiter and Saturn are both gas giants, and the conditions on both of those planets are perfect for the abiotic synthesis of phosphine, meaning it is generated through chemical processes not associated with living organisms. The cores of these planets harbor amounts of pressure and energy sufficient for phosphine generation; afterward, phosphine is pushed to the atmosphere by powerful convection currents. In contrast, the Venusian atmosphere does not have the same degree of heat and energy, and the atoms required to create phosphine, phosphorus, and hydrogen do not often react with each other. Phosphorus quickly reacts with oxygen-containing molecules, such as carbon dioxide, which limits its ability to react with hydrogen. Thus, researchers concluded that the production of phosphine most likely comes from a living creature.

Though very surprising, the presence of phosphine does not immediately indicate life on the hellish planet. There are several inanimate sources of phosphine, including volcanic activity and lightning. The chemical composition of Venus could still be too harsh to sustain life. A detection of phosphine could merely be “anomalous and unexplained chemistry,” said Gerald Joyce, a researcher at the Salk Institute for Biological Studies in California. However, the researchers at MIT who published the discovery believe that nothing other than life could produce the concentrations of phosphine found on Venus. ALMA detected a concentration of 20 parts per billion in Venus’s cloud layer, which is thousands of times greater than the concentrations found on Earth. Furthermore, temperatures in the cloud layer are hospitable, hovering around 86 degrees Fahrenheit.

Research missions to Venus are already being planned in response to the discovery of phosphine. One of them is being run by Rocket Lab, a small, private rocket company based in New Zealand. It is developing a small probe that would be launched from a spacecraft with no parachute or breaks, descend through Venus’s atmosphere, gather phosphine levels, and send data back to the spacecraft before being destroyed by heat and pressure. If the mission is successful, Rocket Lab would be the first private company to launch a mission to another planet. NASA has plans set for traveling to Venus as well. The mission, named DAVINCI+, would also send a probe into the atmosphere to collect concentrations of gases.

While the discovery of phosphine on Venus is opening doors for new research missions, it is also causing scientists to return to older studies and papers regarding hypothetical life on Venus as they are forced to reevaluate its geological and atmospheric behavior. Scientists believe that the planet is still geologically active. Ideas of geological activity also tie into the theory that Venus was once a hospitable planet with a shallow ocean, which eventually evaporated due to its proximity to the sun. The past presence of water could explain the existence of microbes. As the water evaporated and surface temperatures began to rise, the microbes may have risen into the hospitable layer of the atmosphere where phosphine was discovered.

One of the largest concerns for researchers in regards to potentially discovering life on Venus is that models and theories may be too Earth-centric. In the event that life is discovered on Venus, be it photosynthetic microbes, anaerobic microbes, or perhaps something completely unseen, our standard of what we consider “typical” of organisms will have to alter. We’re eager to see if we are not alone in the universe and how our definition of “life” might change if it is discovered. And we are most curious to learn what on Venus could be producing such high amounts of phosphine. Whether or not the existence of phosphine on Venus is a true indication of life, the resulting studies and renewed interest in our “evil twin” planet is sure to deepen our understanding of how to look for extraterrestrial life in the future.