Phosphine gas on Venus could be key to finding alien life

Phosphine is a colorless, flammable, poisonous gas that smells like rotten fish. Humans make it for use in pest control and the production of computer chips. But it is also a waste of a certain type of “abiotic” microbe that lives in oxygen-free environments. His presence is a potential sign that there is something alive.

The gas with the chemical name PH3 has been the center of a heated debate among scientists concerned with life: what it is, what it needs to survive, and where it could be found elsewhere in the universe.

On one side are scientists and their supporters who a year ago claimed to have detected signs of phosphine in the virtually unliveable atmosphere of Venus, the second planet from the sun best known for its boiling surface at 800 degrees Fahrenheit and its thick clouds made not of water, but of acid. Whether intentionally or not, these researchers have raised the alarm that we may have discovered signs of alien life on another world.

On the other side, there are critics who have credibly questioned the science behind the original phosphine claim. And between the two camps sits a powerful mediator: NASA’s top scientist, who recently wrote an article to address the growing argument over highly smelly gas and its possible presence on Venus, and to urge scientists looking for alien life to be a little more careful.

Now a new group of scientists, including some of the team that first put phosphine on Venus, are taking a step back, taking a deep breath, and trying to make sense of what they describe as an important argument. and continuous. A preprint of their article appeared online last week. “One year after the initial announcement, the provisional discovery of PH3 in the clouds of Venus continues to generate a great deal of interest and controversy,” they wrote.

“People might think that the story of Venus’ phosphine is over, that the discovery is debunked or that it is false, that the signal is not there,” Janusz Petkowski, expert in “biosignature gas” at the MIT and co-author of both the original phosphine article and the latest one, told The Daily Beast. “It is not,” added Petkowski. “The history of Venusian phosphine is very much alive and the subject of intense scientific debate.”

In 2019, a team led by astronomer Jane Greaves from Cardiff University in the UK had a hunch. Sifting through images of Venus collected by colleagues scanning the James Clerk Maxwell Telescope in Hawaii, the team saw what they suspected to be the visual signature of phosphine in the dense and toxic atmosphere of Venus.

Greaves’ team therefore requisitioned the large millimeter / submillimeter array of Atacama in Chile and pointed it at Venus specifically to search for phosphine. A year later, in September 2020, the team broke the shocking news to the world: they had found phosphine. And the implications were revolutionary.

There, Greaves and company wrote in Nature, “No currently known abiotic production route [for phosphine] in the atmosphere of Venus, clouds, surface and subsoil, or lightning, volcanic or meteoritic delivery. While the phosphine “could come from an unknown photochemistry or geochemistry”, the best explanation could be “the presence of life”.

Greaves did not immediately respond to a request for comment.

The astronomical community was abuzz with the news. But the excitement quickly turned to skepticism. “The community still views Venus as the least likely home in life,” explained Petkowski and his co-authors. Europe and Enceladus, respectively the moons of Jupiter and Saturn, appear to be more favorable to microbes, as do Mars and Titan, another moon of Saturn.

“This skepticism arises from the fact that the Venusian environment presents many challenges to life as we know it,” the Petkowski team wrote. Namely, there is the fact that Venus is enveloped in clouds of sulfuric acid.

Doubt deepened in some quarters as scientists verified the work of Greaves’ team. Some have pointed out that ALMA is not the best instrument for inspecting an object as bright as Venus. The review forced Greaves and the company to recheck their data and release some minor corrections to their original document.

“Our discovery of phosphine in the clouds of Venus has sparked much debate,” they acknowledged. But they maintained their conclusion that there might be phosphine on Venus, and that could be evidence of “life in a hyperacid aerial biosphere.”

The argument raged, to the point where Jim Green, NASA’s chief scientist, felt compelled to intervene. In an article published in Nature on October 27, Green proposed what he described as a “framework for reporting evidence of life beyond Earth.”

“Our generation could realistically be the one to discover evidence of life beyond Earth,” Green wrote. “With this privileged potential comes responsibility.” To avoid premature claims based on superficial research, the NASA scientist urged his colleagues – as well as members of the press – to maintain the allegations of alien life up to a seven-step scale of evidence from level an (interesting) at level seven (final).

Venusian phosphine is still a “level one measure,” Green told The Daily Beast. “Why would we promote it or talk about it like it’s a level five event?” “

“The breadth of the question of whether we are alone in the universe, and the public interest in it, opens up the possibility that the results may be considered to imply more than what the observations support or what the observers don’t hear it, ”Green wrote. In other words, scientists should think long and hard before insisting that they have found evidence of aliens, even if it is just microbes. It’s too important to be wrong.

It’s not at all clear Greaves and his team made be wrong, pointed out Petkowski and his colleagues. After looking at Greaves’ data in different ways, they concluded “There is strongly suggestive evidence from two independent methods that there is phosphine in the clouds of Venus.”

The next question, of course, is where does the phosphine come from? There is no consensus that phosphine “can be made by natural processes,” Harvard University physicist Avi Loeb told The Daily Beast.

Some scientists believe the gas detected by Greaves and his team could, in part, be a byproduct of volcanic eruptions. “Although the original Greaves phosphine study [and her team] estimated that the amount of phosphine detected is far too high to be solely due to volcanic eruptions, they would certainly contribute if they are currently occurring on Venus, ”said Siddharth Krishnamoorthy, planetologist at NASA’s Jet Propulsion Laboratory in California, at Daily. Beast.

In addition to volcanoes, Petkowski and his co-authors evaluated all other possible major non-biological sources of phosphine on Venus: lightning, meteor impacts, solar wind, and bizarre chemical processes in the atmosphere.

None made much sense, they wrote. “None of the processes examined produced sufficient amounts of PH3 to account for the observed abundance ….” This is in line with what the Greaves investigation initially concluded last year.

This does not necessarily mean that there must be life on Venus. This makes mean that, despite the skepticism in some corners of the astronomical world, we cannot yet rule out the possibility of life on Venus. “A chemical explanation seems more likely, but biology should not be ruled out as a possible explanation,” Dirk Schulze-Makuch, astrobiologist at the Technical University of Berlin, told The Daily Beast.

Yes, Venus is wicked for life as we know it. But it might just be for a life form we don’t currently know about. Life might have found a way to adapt to this planet’s acidic atmosphere, Schulze-Makuch said.

It will take a lot more exploration and much deeper observation to understand what is going on in the acid clouds of the second planet from the sun. Petkowski and his team don’t think we’ll get a real resolution to the phosphine issue until we study it directly. In other words, we have to send a probe to Venus.

Fortunately, there are two in development. The Deep Atmosphere Venus Investigation of Noble gas, Chemistry and Imaging, or DAVINCI + mission, aims to scan the atmosphere of Venus with a spherical probe that will dive into the planet’s atmosphere, sampling the unbreathable air “to understand why the atmosphere of Venus is a greenhouse. compared to that of Earth, ”according to NASA.

Around the same time, the separate Venus Emissivity, Radio Science, InSAR, Topography and Spectroscopy – or VERITAS – probe will orbit Venus and use its on-board radar and infrared sensor to scan the planet.

The probes should be launched around 2029 and arrive on Venus a few years later. Maybe then we can finally begin to settle the argument that began a year ago with a bold claim about curious gas on a seemingly inhospitable planet.