With scientists recently discovering the presence of phosphine in the atmosphere of Venus, two members of the Rutgers community discussed how this discovery came to be and what it means for potential life on Venus.
Nathan Yee, an astrobiologist and professor in the Department of Environmental Sciences, said that on Earth, all living things known to science require phosphorus, as it is an essential life element existing in nature in different oxidation states.
In its most oxygenated form, it exists as a compound called phosphate which is found in our bones and DNA, he said. When oxygen is taken away, phosphorus adapts to a lower redox state and becomes phosphite.
When the redox potential is increased even more, meaning that oxygen decreases to vanishingly low levels, then the extremely reduced gaseous phase of phosphorus called phosphine is able to form, he said.
Jihua Hao, a postdoctoral researcher at Rutgers in theoretical and experimental geochemistry, said the discovery of phosphine in Venus’ atmosphere had not been speculated about previous to its discovery due to the fact that the atmosphere of Venus is very oxidizing, an oxygen-rich environment. While in contrast, phosphine forms in environments free of oxygen, he said.
Its presence was observed by a powerful telescope in Hawaii as scientists were making observations of Venus, and from the light reflecting off of the planet, they were able to deduce the presence of this gaseous phosphorus compound, Yee said.
Hao said this was done through spectral analysis as the absorption spectra of light reflecting off of the planet were analyzed and a signal in the region was found for phosphine and sulfur dioxide.
The signal was too strong for it only to be sulfur dioxide, meaning that another compound had to be present. After more spectral analysis, it was determined that the signal of phosphine was indeed present, he said.
“What this new discovery on Venus tells me, is that there is a completely different phosphorus cycle on Venus than Earth,” Yee said. “And that is enough scientific justification to go back to Venus in future (National Aeronautics and Space Administration) NASA missions to probe the atmosphere of Venus to understand its phosphorus cycle.”
Venus’ conditions and atmosphere are much different from the Earth’s, as Venus has an extremely hot and volcanic surface with a dry atmosphere rich in sulfuric acid, Hao said.
These conditions of acidity and lack of water activity are highly problematic for the sustaining of life, but he said that in some regions of Venus’ atmosphere, the climate is habitable with temperatures reaching approximately 30 degrees Celsius.
“I’m highly suspicious of the life there, but if there’s life there, this active phosphorus cycle may supply some phosphorus for them to live,” Hao said.
In regards to the conditions of the atmosphere, Yee said the potential life with the ability to withstand these challenging factors could be microbes that can live in acid, called acidophiles, along with microbes known to live in extremely low water activity that transform their cells into spores in order to survive the dry conditions.
Yee said another theory is that the presence of phosphine comes from volcanic activity on Venus instead of being of biological origin. The interior of Venus contains phosphorus, and depending on how much oxygen is present in the interior, there might be some phosphate that erupts in lava that makes phosphorus minerals, he said.
If deficient in any oxidants, it actually may make phosphine, meaning that the source of this reduced phosphorus gas could be originating from the mantle of Venus.
Hao said if the phosphine comes from volcanoes, it may indicate that the interior of Venus has less abundance of oxidants than the Earth, meaning that it has a more reducing environment which would allow some subsurface microbes to grow in a cooler region, according to his original hypothesis.
Instead of being a sign of life, phosphine could be a source of food for microorganisms living on the surface of Venus, he said. “Maybe biology can use that thermodynamic disequilibrium to allow them to thrive in some locations,” Hao said.
The evolutionary history of Venus could reveal unknowns about Venus’ phosphorus cycle, Hao said, as Venus’ harsh conditions now do not necessarily mean that those conditions were the same in the past or will always be the same.
“If life is discovered on Venus, there are so many questions we can ask. Did life evolve once and have a common origin with Earth, or did life evolve independently and there were multiple genesis events in the solar system, which would have profound implications for life in the universe,” Yee said.
“I think it’s coming from volcanoes, but there are certain scientists that think that the phosphine is coming from microorganisms living in the clouds of Venus. And if that’s detected, that would transform our understanding of life in the universe,” he said.