Recent observations of Venus have provided new evidence of a compound in its atmosphere that could indicate the presence of life, in findings that potentially lend weight to controversial past discoveries.
Phosphine, a toxic gas that may be associated with life on rocky planets, was first detected in Venus’ atmosphere four years ago, a surprise discovery. Now, new observations potentially reinforce those earlier findings, hinting at biosignatures that, if confirmed, could mean life forms are able to thrive in the planet’s harsh environment.
A controversial discovery on Venus
The first detection of phosphine in Venus’ oxidized atmosphere was reported in September 2020, when a team of scientists led by Jane Greaves of Cardiff University reported finding evidence of the toxic molecule. The discovery initially sparked debate about whether life could exist on Venus, as phosphine is normally associated with organisms that thrive in oxygen-poor environments.
The team’s announcement received considerable media attention and also sparked controversy that resulted in rebukes from some members of the scientific community. Perhaps the most scathing criticism came from the organizing committee of the International Astronomical Union’s (IAU) Commission F3 on Astrobiology, which even questioned the ethics of Greaves and his team in the way the discovery was revealed.
“It is the ethical duty of every scientist to communicate with the media and the public with great scientific rigor and to be careful not to exaggerate an interpretation that will be irremediably taken up by the press,” the commission wrote in an official statement published at the time.
The commission added that it “would like to remind relevant researchers that we need to understand how the press and media behave before communicating with them.”
Early follow-up attempts to detect the compound again were unsuccessful. However, last year, Greaves and his team managed to detect phosphine in deeper parts of the planet’s atmosphere during observations with the James Clark Maxwell Telescope (JCMT) at the Mauna Kea Observatory in Hawaii. Additional detections with NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) also suggested the presence of phosphine, which could be coming either from inside or below Venus’ clouds.
Interestingly, a separate research effort led by Rakesh Mogul of California Polytechnic State University reanalyzed data obtained by NASA’s Pioneer Venus Large Probe in 1978, revealing additional support for the presence of phosphine in the planet’s atmosphere that appeared to be consistent with earlier findings.
“To date, our analyses remain uncontested in the literature,” Mogul said of his team’s findings, which he called “in sharp contrast to the telescopic observations” made by Greaves and his colleagues, which Mogul said “remain controversial.”
New discoveries always call for caution
Using a new receiver on the James Clerk Maxwell telescope, Greaves and his colleagues say they have collected up to 140 times more data than previous observations, including additional detections of phosphine. The new findings were revealed in two presentations by Greaves and David Clements, a researcher at Imperial College London who was involved in the discovery, on July 17 at a meeting of the Royal Astronomical Society.
However, the discovery of ammonia in Venus’ atmosphere may be even more interesting in the search for possible life forms on Venus. Clements called the discovery “more significant than the discovery of phosphine.” The 2021 study by Mogul and colleagues also determined that ammonia could potentially exist in Venus’ atmosphere.
Despite the potential significance of the discovery, during Greaves’ lecture at the Society’s meeting earlier this month, a slide from his presentation stressed that there are “many important unknowns about the Venusian surface and atmosphere,” adding that “even a ‘gold standard’ discovery of two “Bio-associated molecules are not proof of the existence of life!”
Likewise, Clements told CNN that it would be premature to speculate that these gases indicate the existence of life on Venus, although he conceded that the presence of ammonia along with the phosphine certainly strengthens that possibility.
Promising preliminary results
While cautioning against jumping to conclusions, Greaves explained in his presentation this month that there is at least a possibility that organisms on Venus could produce ammonia to help reduce the acidity of the environment and thus make it more habitable. If that were the case, Greaves and his colleagues speculate that the gas could potentially have risen into the atmosphere, allowing its detection.
“Ammonia has been detected in the upper clouds, where temperatures are -15°C or lower and it is probably too cold for life to exist,” reads a post on the Royal Astronomical Society’s official X account summarizing Greave’s presentation.
“The researchers want to see if the molecule is also present deeper in the clouds of Venus, where it is much warmer,” he adds.
The Venus session gets even more exciting! @jgreaves6 A Cardiff University study reveals that in addition to phosphine, a second potential biomarker gas – ammonia – has been tentatively detected in the clouds of Venus.
Again, it is important to emphasize that these are preliminary results. pic.twitter.com/pxptIkTzxF
— Royal Astronomical Society (@RoyalAstroSoc) July 17, 2024
In the future, more evidence will be needed, which could be obtained in several ways. One possibility is to collect data by NASA’s Deep Atmosphere Venus Investigation of Noble Gases, Chemistry, and Imaging (DAVINCI) mission, which will send a probe into Venus’ harsh environment to measure its atmosphere in 2029.
Another potential opportunity to take measurements of the planet’s atmosphere could come from the European Space Agency’s Jupiter Icy Moons Explorer, which will pass by Venus next year and is equipped with instruments that could potentially obtain useful data that could complement the findings of Greaves and his colleagues.
Until these data are obtained, however, the new findings remain inconclusive, although promising.
“Again, it is important to emphasize that these are preliminary results,” the Society said in its X release.
Micah Hanks is the editor and co-founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work on micahhanks.com and on X: @MicahHanks.