Scientists have found, in the absence of actual life forms, phosphine gas in the inhospitable clouds of Venus that is being created as fast as it is being destroyed.
The atmosphere of Venus contains traces of phosphine gas, which on Earth is associated with living organisms.
Scientists said on Monday, in fresh insight into conditions on our nearest planetary neighbour, that an international team first spotted the phosphine using the James Clerk Maxwell Telescope in Hawaii and confirmed it using the Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile.
Writing in Nature Astronomy, the team stressed that the presence of phosphine alone did not prove the presence of life on Venus.
However, as the clouds swirling about its broiling surface are highly acidic and therefore destroy phosphine very quickly, the research did show that something was creating it anew.
The researchers conducted several modelling calculations in a bid to explain the new phosphine production.
They concluded that their research provided evidence "for anomalous and unexplained chemistry" on Venus.
"I was very surprised – stunned, in fact," said astronomer Jane Greaves of Cardiff University in Wales, lead author of the research published in the journal Nature Astronomy.
Phosphine is to Venus as methane is to Mars? 20 parts-per-million of phosphine have been detected in the temperate clouds of Venus, and its source is not evident. Greaves et al.: https://t.co/aZhuAXkNdZ pic.twitter.com/a3sFW6qXoS— Nature Astronomy (@NatureAstronomy) September 14, 2020
We are looking for signs of life on exoplanets by looking for gases that we don't expect to be there, and there are many missions looking for potential signs for life in our own Solar System, says @ProfSaraSeager #VenusNews— Royal Astronomical Society (@RoyalAstroSoc) September 14, 2020
Possibility of extraterrestrial life
The existence of extraterrestrial life long has been one of the paramount questions of science. Scientists have used probes and telescopes to seek "biosignatures" –– indirect signs of life –– on other planets and moons in our solar system and beyond.
"With what we currently know of Venus, the most plausible explanation for phosphine, as fantastical as it might sound, is life," said Massachusetts Institute of Technology molecular astrophysicist and study co-author Clara Sousa-Silva.
"I should emphasise that life, as an explanation for our discovery, should be, as always, the last resort," Sousa-Silva added. "This is important because, if it is phosphine, and if it is life, it means that we are not alone. It also means that life itself must be very common, and there must be many other inhabited planets throughout our galaxy."
Phosphine, a phosphorus atom with three hydrogen atoms attached, is highly toxic to people.
Earth-based telescopes like those used in this research help scientists study the chemistry and other characteristics of celestial objects.
Phosphine was seen at 20 parts-per-billion in the Venusian atmosphere, a trace concentration.
Greaves said the researchers examined potential non-biological sources such as volcanism, meteorites, lightning and various types of chemical reactions, but none appeared viable. The research continues to either confirm the presence of life or find an alternative explanation.
Venus is Earth's closest planetary neighbour. Similar in structure but slightly smaller than Earth, it is the second planet from the sun. Earth is the third. Venus is wrapped in a thick, toxic atmosphere that traps in heat. Surface temperatures reach a scorching 880 degrees Fahrenheit (471 degrees Celsius), hot enough to melt lead.
"I can only speculate on what life might survive on Venus, if indeed it is there. No life would be able to survive on the surface of Venus, because it is completely inhospitable, even for biochemistries completely different from ours," Sousa-Silva said.
"But a long time ago, Venus could have had life on its surface, before a runaway greenhouse effect left the majority of the planet completely uninhabitable."
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You think the coronavirus pandemic is the biggest news of the year? Today there will be a stunning announcement about #phosphine in #Venus, hinting - as far as we know - that there would likely be microbial life in the clouds of our next-door neighbor! WOW! #astrobiology pic.twitter.com/JdTugz75rv— Mika Mäkeläinen (@Mikareport) September 14, 2020
The acid test
Some scientists have suspected that the Venusian high clouds, with mild temperatures around 30 degrees Celsius (86 degrees Fahrenheit), could harbour aerial microbes that could endure extreme acidity. These clouds are around 90 percent sulphuric acid. Earth microbes could not survive that acidity.
"If it's microorganisms, they would have access to some sunlight and water, and maybe live in liquid droplets to stop themselves dehydrating, but they would need some unknown mechanism to protect against corrosion by acid," Greaves said.
On Earth, microorganisms in "anaerobic" environments, ecosystems that do not rely on oxygen, produce phosphine. These include sewage plants, swamps, rice fields, marshlands, lake sediments and the excrements and intestinal tracts of many animals. Phosphine also arises non-biologically in certain industrial settings.
To produce phosphine, Earth bacteria take up phosphate from minerals or biological material and add hydrogen.
"We have done our very best to explain this discovery without the need for a biological process. With our current knowledge of phosphine, and Venus, and geochemistry, we cannot explain the presence of phosphine in the clouds of Venus. That doesn't mean it is life. It just means that some exotic process is producing phosphine, and our understanding of Venus needs work," Clara Sousa-Silva said.
Venus should be hostile to phosphine. Its surface and atmosphere are rich in oxygen compounds that would rapidly react with and destroy phosphine.
"Something must be creating the phosphine on Venus as fast as it is being destroyed," said study co-author Anita Richards, an astrophysicist associated with the University of Manchester in England.
While previous robotic spacecraft have visited Venus, a new probe may be needed to confirm life.
"Fortunately, Venus is right next door," Sousa-Silva said. "So we can literally go and check."