The Possibility of Life on Venus
A picture of Venus taken on September 15, after the discovery of phosphine within its atmosphere. (NASA)
An international team of astronomers recently discovered phosphine in Venus’s atmosphere on September 14. While the evidence is inconclusive, scientists are now re-evaluating the possibility of life existing on Venus, even though the planet was once deemed inhabitable.
Venus experiences a runaway greenhouse effect: dense clouds in the atmosphere fill up with carbon dioxide and trap sunlight. This effect causes temperatures on Venus’s surface to skyrocket to temperatures between 800-900 degrees Fahrenheit. The dense Venusian clouds primarily contain sulfuric acid, which is likely lethal to Earth-like life forms without protective shells.
Although there have been dozens of attempts to explore Venus in the past, the gaseous atmosphere melts the metal of any spacecraft trying to land on its surface. Currently, Japan’s spacecraft Akatsuki is the only probe orbiting Venus.
Scientists Carl Sagan and Harold Morowitz co-authored a paper in 1967 examining the possibility of life on Venus. Billions of years ago, Venus was covered in water. As the water evaporated due to heat-trapped gases increasing the temperature of Venus’s surface, Sagan and Morowitz theorized that life forms could have adapted and eventually learned to live in the skies.
Dr. Jane Greaves, an astronomer at Cardiff University in Wales, became intrigued by the idea of phosphine as a biosignature, or a substance that provides evidence of life. She went to Hawaii to observe Venus for any indications of phosphine in its atmosphere. After sharing her findings with Dr. Clara Sousa-Silva, an MIT scientist who studies phosphine, the two began an inquiry about the possibility of life on Venus.
About 31 miles above Venus’s surface, the temperature and pressure reach a habitable level by Earth’s standards. Drs. Greaves and Sousa-Silva detected the phosphine molecules within these levels of Venus, in accordance with Sagan and Morowitz’s theory.
Phosphine typically dissipates due to the acidic nature of the Venusian atmosphere with clouds made of sulfuric acid droplets. Therefore, some type of chemical process must be replenishing the phosphine for it to aggregate in such high quantities.
A graphic representation of phosphine molecules with Venus’s atmosphere. Phosphine is a combination of three hydrogen atoms and one phosphorus atom. Forming this molecule does not require the presence of life. Immense heat and pressure can force the atoms to come together and form phosphine, such as on Jupiter and Saturn (Phys Org)
Through computer simulations, Dr. Sousa-Silva and her team replicated Venusian conditions, including lightning strikes and meteor crashes. However, nothing within the simulations produced enough energy to account for the high quantity of phosphine.
According to modern scientific knowledge, phosphine only exists in three places: swamps, marshlands, or inside the intestines of small animals. Violent storms, the strength of which has not been observed elsewhere in the cosmos, also produce phosphine on Saturn and Jupiter. Now scientists have observed the chemical compound on Venus.
Both the coronavirus and Venus’s limited time above Earth’s horizon hindered Dr. Greaves and Dr. Sousa-Silva from continuing their research. After ruling out all other possibilities, the team concluded that the phosphine was either a sign of life or a foreign chemical reaction.
Dr. Sousa-Silva commented, “I’m skeptical. I hope that the whole scientific community is just as skeptical, and I invite them to come and prove me wrong, because we’re at the end of our expertise.” The only way to ensure life exists on Venus is to go there! And make more detailed measurements, of course.