(CNN) – Four years ago, the unexpected discovery in the clouds of Venus of a gas that on Earth is a sign of life – phosphine – sparked controversyand won reviews in later observations that did not agree with his findings.
Now, the same team that made that discovery is back with more observations, first presented on July 17 at a meeting of the Royal Astronomical Society in Hull, England. Over time, they will form the basis of one or more scientific studies, and that work has already begun.
The data, according to the researchers, contains even stronger evidence that phosphine is present in the clouds of Venus, our closest planetary neighbor. sometimes called Earth’s evil twinthe planet is similar to ours in size but has surface temperatures that can melt lead and clouds made of corrosive sulfuric acid.
The work benefited from a new receiver installed on one of the instruments used for the observations, the James Clerk Maxwell Telescope in Hawaii, giving the team more confidence in their findings. “There is also a lot more data,” explains Dave Clements, reader in astrophysics at Imperial College London.
“We had three observation campaigns and, in just one, we obtained 140 times more data than in the original detection,” he explained. “And what we have so far indicates that we are once again having phosphine detections.”
Another team, of which Clements is also a part, presented evidence of another gas, ammonia.
“That is possibly more significant than the discovery of phosphine,” he added. “We are very far from affirming it, but if there is life on Venus producing phosphine, we have no idea why it produces it. However, if there is life on Venus producing ammonia, we do have an idea why it might want to breathe ammonia.”
On Earth, phosphine is a smelly, toxic gas produced by decaying organic matter or bacteria, while ammonia is a pungent-smelling gas that occurs naturally in the environment and is also produced in its environment. mostly by bacteria at the end of the decomposition process of plant and animal waste.
“Phosphine was discovered in Saturn’s atmosphere, but that’s not unexpected, because Saturn is a gas giant,” Clements said. “There is a lot of hydrogen in its atmosphere, so hydrogen-based compounds, like phosphine or ammonia, are the ones that dominate there.”
However, rocky planets like Earth, Venus, and Mars have atmospheres where oxygen dominates the chemistry, because they didn’t have enough mass to hold the hydrogen they had when they originally formed, and that hydrogen escaped.
Finding these gases on Venus is therefore unexpected. “By all normal expectations, they shouldn’t be there,” Clements said. “Both phosphine and ammonia have been suggested as biomarkers, even on exoplanets. So finding them in the atmosphere of Venus is also interesting for that reason. “When we published the phosphine findings in 2020, it was understandably a surprise.”
Later studies questioned the results, suggesting that phosphine was actually sulfur dioxide ordinary. Data from instruments other than those used by Clements’ team – such as the Venus Express spacecraftthe Infrared Telescope Facility of the POT and the now defunct airborne observatory SOFIA– they also failed to replicate the phosphine findings.
But Clements said his new data, from the Atacama Large Millimeter/submillimeter Array, or ALMA (for its acronym in English), rule out that sulfur dioxide could be a contaminant and that the absence of phosphine in other observations is due to timing. “It turns out that all of our observations that detected phosphine were taken when Venus’s atmosphere was passing from night to day,” he said, “and all of the observations that did not find phosphine were taken when the atmosphere was passing from day to night.”
During the day, ultraviolet light from the Sun can break down molecules in Venus’ upper atmosphere. “All phosphine decays, and that’s why you don’t see it,” Clements said, adding that the only exception was the Stratospheric Infrared Astronomy Observatory, which made observations at night. However, closer analysis of the data by Clements’ team revealed faint traces of the molecule, bolstering the theory.
Clements also noted a investigation unrelated group from a group led by Rakesh Mogul, professor of chemistry and biochemistry at California Polytechnic State University, Pomona. Mogul reanalyzed old probe data Pioneer Venus Large Probe from NASA, which entered the planet’s atmosphere in 1978.
“It showed phosphine within the clouds of Venus at around the parts per million level, which is exactly what we’ve largely been detecting,” Clements said. “So it’s starting to come together, but we still don’t know what’s causing it.”
Using data from the Pioneer Venus Large Probe, the Mogul-led team published a “convincing case for phosphine deep in the (Venus) cloud layer” in 2021, Mogul confirmed in an email. “To date, our analyzes remain undisputed in the literature,” said Mogul, who was not involved in Clements’ team’s research. “This is in stark contrast to telescopic observations, which remain controversial.”
Ammonia on Venus would be an even more surprising discovery. Presented at the Hull talks by Jane Greaves, professor of astronomy at Cardiff University, UK, the findings will form the basis of another scientific paper, using data from the Green Bank Telescope in West Virginia.
The clouds on Venus are made up of droplets, Clements explained, but they are not water droplets. There is water in them, but also so much dissolved sulfur dioxide that they become extremely concentrated sulfuric acid, a highly corrosive substance that can be fatal to humans with severe exposure. “It is so concentrated that, as far as we know, it would not be compatible with any type of life that we know on Earth, including Extremophilic bacteria, which like very acidic environments,” he said, referring to organisms capable of surviving in extreme environmental conditions.
However, the ammonia contained in these acid droplets can act as a buffer against the acidity and reduce it to a level low enough that some known terrestrial bacteria could survive in it, Clements added.
“The most interesting thing would be if ammonia were produced by some form of microbial life, as it would be a great way to regulate its own environment,” Greaves explained at the Royal Astronomical Society talks. “It would make your environment much less acidic and much more survivable, to the point where it’s only as acidic as some of the most extreme places on Earth, so it’s not completely crazy.”
The role of ammonia, in other words, is easier to explain than that of phosphine. “We understand why ammonia can be useful for life,” says Clements. “We don’t understand how ammonia is produced, just as we don’t understand how phosphine is produced, but if there is ammonia there, it would have a functional purpose that we can understand.”
However, Greaves warned that even the presence of phosphine and ammonia would not be proof of microbial life on Venus, because much information about the state of the planet is missing. “There are many other processes that could take place, and we don’t have the ground truth to say whether that process is possible or not,” he said, referring to compelling evidence that can only come from direct observations from inside the atmosphere. of the planet.
One way to carry out such observations would be to convince the European Space Agency to turn on some instruments aboard the probe. Jupiter Icy Moons Explorerwhich is headed to the Jupiter system when it passes Venus next year. But the data would be even better with DAVINCI, an orbiter and atmospheric probe that NASA plans to launch to Venus. in the early 2030s.
From a scientific perspective, the new data on phosphine and ammonia are intriguing, but warrant cautious optimism, says Javier Martín-Torres, professor of planetary sciences at the University of Aberdeen in the United Kingdom. Martín-Tres led a study published in 2021 which questioned the findings on phosphine and postulated that life is not possible in the clouds of Venus.
“Our paper emphasized the harsh and seemingly inhospitable conditions of Venus’ atmosphere,” Martín-Torres said in an email. “The discovery of ammonia, which could neutralize sulfuric acid clouds, and phosphine, a possible biosignature, challenges our understanding and suggests that more complex chemical processes could be at play. “It is crucial that we address these findings with careful and thorough scientific investigation.”
The findings open new avenues of research, he added, but it is essential to treat them with a healthy dose of skepticism. Although the detection of phosphine and ammonia in the clouds of Venus is exciting, it is just the beginning of a long journey to unravel the mysteries of that planet’s atmosphere, he said.
Scientists’ current knowledge of Venus’ atmospheric chemistry cannot explain the presence of phosphine, said Dr. Kate Pattle, a professor in the department of physics and astronomy at University College London. “It is important to note that the team behind the phosphine measurements does not claim to have found life on Venus,” Pattle said in an email. “If phosphine is indeed present on Venus, it could indicate life, or it could indicate that there is Venusian atmospheric chemistry that we do not yet understand.”
