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New preliminary evidence of phosphine and ammonia in the atmosphere of Venus sheds light on the mystery behind the production of these gases. Given the now formidable origins of phosphine and ammonia, the idea that these chemicals may have a biological source on Venus is being seriously considered by some scientists.
Venus doesn’t seem like a habitable place because of its blisteringly hot surface temperatures sufficient to melt lead and terrible surface pressure. The presence of phosphine and ammonia in the clouds of the second planet from the sun and the hottest planet in the solar system suggests that if life could exist, it would be found high above the surface of Venus.
A team led by Jane Greaves of Cardiff University made the new detections of phosphine and ammonia using sub-millimetre radio wavelength data collected by the James Clerk Maxwell Telescope (JCMT) in Hawaii and the Greenbank Telescope in West Virginia.
“We don’t know how you make phosphine or ammonia in an oxygenated atmosphere like Venus,” said team member and astrophysicist Dave Clements of Imperial College, London, in an interview with Space.com. Then again, it’s not clear why biology on Earth produces phosphine either.” Whether it’s in penguin pee or badger guts, we don’t know why bacteria make phosphine, but they do. “
Related: Life on Venus? Interesting molecule phosphine appears in planetary clouds again
Detection of phosphine over Venus creates controversy
The initial JCMT detection of phosphine on Venus in 2020 by Greaves and his team was met with fierce disagreement from some quarters.
This disagreement centered on how the data was processed and whether this was creating false signals since observations at other telescopes had difficulty detecting the phosphine.
Clements said those technical disagreements have now been resolved and the latest measurements, using a new detector on the JCMT called Nāmakanui (meaning ‘Big Eyes’ in Hawaiian), came from three observing campaigns, each at providing 140 times as much data as the initial detection.
Clements said those technical disagreements have now been resolved and the latest measurements, using a new detector on the JCMT called Nāmakanui (meaning ‘Big Eyes’ in Hawaiian), came from three observing campaigns, each at providing 140 times as much data as the initial detection.
“Nāmakanui is a series of three different receivers at three different frequencies,” said Clements.
One of those receivers, called ‘Ū’ū (the name of a particular big-eyed fish that can be seen in the dark in the waters around Hawaii), is capable of phosphine, as well as sulfur dioxide and “semi-heavy water ” to detect (HDO), water with three hydrogen atoms instead of two and the usual one oxygen atom. Sulfur dioxide and HDO change over time in the clouds of Venus, and Greaves and Clements’ team want to see how phosphine also changes.
“There are suspicions, possibilities, that the amount of phosphine could vary over time, but we don’t know what drives the variation,” said Clements.
One possibility is that ultraviolet light from the sun breaks up molecules in the upper atmosphere of Venus, causing variation in phosphine.
Clements pointed out that the initial detection of phosphine came when JCMT was observing the morning Terminator on Venus, where the planet’s nights were turning towards it. At night, the sun’s ultraviolet light would not be affected, allowing phosphine to build up.
The other observations, from the European Space Agency’s Venus Express spacecraft, SOFIA (Stratospheric Observatory for Infrared Astronomy), and NASA’s Infrared Telescope Facility in Hawaii, observed Venus as day turned to night, and could solar ultraviolet has already broken up much. of phosphine, so they struggled to detect it.
Clements has since re-analyzed the SOFIA data and found a small hint that phosphine is present. Rakesh Mogul at California Polytechnic State University found that it was also rich in phosphorus while reanalyzing mass spectrometer data from the old 1978 Pioneer Venus mission.
“If phosphine is being destroyed by solar ultraviolet, that’s consistent with these other observations that it’s not being found,” Clements said. It also suggests that the phosphine is being rapidly replenished by some unknown process.
Then there is the ammonia.
Could ammonia make Venus more habitable?
Detected at Venus by the Green Bank radio telescope, the origin of ammonia is as murky as that of phosphine. If its presence in the atmosphere of Venus is real, however, it could give microbial life a way to survive in the extreme conditions there.
One obstacle to imagining how life could survive in the atmosphere of Venus is the acidity of the environment, with clouds of pure sulfuric acid. Although the temperature at an altitude of 31.6 to 38.5 miles (51 to 62 kilometers) is moderate, compared to the sweltering 870 degrees Fahrenheit (465 degrees Celsius) on the surface, no one can see how life could survive on the acidity.
Ammonia provides a way for life to do that. When mixed with sulfur dioxide, the ammonia neutralizes some of the acidity.
“It’s still horrifyingly acidic,” Clements said. “But it makes the droplets compatible at least with some acidophilic extremophile life that we know exists on Earth.”
That recent discovery supported life’s ability to survive under those conditions amino acids can remain stable among high concentrations of sulfuric acid.
It is still possible that phosphine and ammonia detected around Venus have a more precise explanation. After all, both are found in the atmospheres of gas giants Jupiter and Saturn.
On these solar system gas giants, these chemicals are formed deep in the hydrogen atmosphere under very high pressure and high temperature conditions before being carried to the clouds by upward convection currents.
The problem is that we would expect phosphine (made of phosphorus with three hydrogen atoms) and ammonia (made of one nitrogen atom with three hydrogen atoms) in hydrogen-rich atmospheres like those of Jupiter and Saturn.
“But if you’re in an oxygenated atmosphere, like Venus or World, everything should be connected to oxygen,” Clements said. “As soon as you have any free hydrogen, it’s going to react with something that’s oxygen-related. We haven’t investigated the chemical ways to produce ammonia like we did with phosphine because the result is so new, but I fully expect it to be the same problem.”
Clements is open to the possibility that phosphine and ammonia are produced by some rare photochemistry in the upper atmosphere of Venus that involves solar ultraviolet breaking up molecules and allowing phosphine and ammonia to form from the molecular debris. If that is the case, no one has observed this process yet, not even in the laboratory.
Another possibility mentioned is that the phosphine could be produced by Volcanoes of Venus.
Related Stories:
— Life on Venus? Interesting molecule phosphine appears in planetary clouds again
— If Venus had Earth-like plate tectonics in the past, did it also have life?
— The Magellanic Clouds must be renamed, astronomers say
Clements also pointed out that the European Space Agency Explorer of Jupiter’s Icy Moons (JUICE) will fly over Venus in August 2025 to help slingshot it towards the Jovian system. JUICE carries instruments capable of detecting phosphine and ammonia, but there is no guarantee that its instruments will be turned on and deployed at Venus.
“We’re still trying to convince the engineers, they don’t like to turn things around mid-flight,” said Clements.
Thus, phosphine and ammonia in the atmosphere of Venus may remain debatable, even controversial, for some time to come. Because of the potential implications for life, the stakes could not be higher.
The team’s findings have not yet been peer-reviewed or published. Although they have yet to be scrutinized by other scientists, they were previewed in a presentation at the 2024 National Astronomy Meeting in the UK in July.
