In September 2020, scientists reported detecting signs of the molecule phosphine in the clouds of Venus. This chemical is a product of either photochemistry or organic matter and a promising sign of life.
But the presence of phosphine on Venus is hotly debated, with some scientists questioning whether or not the chemical compound was truly detected or not. Some experts also ask whether life is the only possible origin for phosphine on the planet.
A new study, titled "Volcanically extruded phosphides as an abiotic source of Venusian phosphine," published in the Proceedings of the National Academy of Sciences (PNAS), has shown that this mysterious chemical in the Venusian atmosphere might not be a sign of life but due to volcanism on Venus.
Detecting Signs of Life on Venus
Professor Jane Greaves from Cardiff University reported early last fall the discovery of phosphine on the Venusian atmosphere based on the data from the James Clerk Maxwell Telescope (JCMT) and Atacama Large Millimeter Array (ALMA).
Phosphine is a compound that quickly decays, its presence on Venus could have meant that there must be an ongoing process of replenishing it. The compound can also be seen in Jupiter due to its enormous gravity, pressure, and high heat. But the compound is rarely detected in small rocky planets like Venus.
The sheer amount of phosphine detected on the planet seemed to suggest that volcanoes were not sufficient to be the source of the gas, Universe Today reported. Greaves and her team carefully ruled out geological processes before announcing that they could come from alien life.
It attracted the attention of the scientific community, and so some experts have explored the claim. But oftentimes, these new studies complicated the picture. Some suggested that the phosphine that Greaves and her team detected might have been sulfur dioxide in a different layer of the Venusian atmosphere.
Eventually, the follow-up studies settled on the position that life on Venus could be possible but in lower quantities, unlike the study claims. These studies opened for an alternative to the biological hypothesis on the Venusian volcanoes.
No Life on Venus?
The team of scientists in the new study found that volcanism on Venus might explain the small amounts of phosphides from deep in the planet's mantle. They explain that volcanic eruptions could spew these chemicals in volcanic dust into the atmosphere, react to sulfuric acid, and form phosphine.
They suggest that a volcanic eruption in the scale of the Krakatau eruption on Earth in 1893 was necessary for phosphide to reach altitudes necessary for the previously reported phosphine detection, Space.com reported.
The team said that the fluctuations in the amount of haze seen above the clouds might possess enough ongoing volcanic activity to generate that much amount of phosphine to be detected by the previous research.
Study senior author and planetary Jonathan Lunine at Cornell University told Space.com that: "Venus looks like a volcanic planet — it has a very youthful surface, and there is evidence it has experienced substantial resurfacing recently in its history."
They noted that future data from ALMA and other observatories could tell whether the presence of phosphine on Venus is indeed a sign of life or due to volcanism. There are also more Venus missions now, which will hopefully help clear this uncertainty.
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