The sudden discovery of phosphine, a foul-smelling gas produced by microbes on planet Earth, in Venus' atmosphere could spark a revolution in astrobiology..
The upper surfaces of clouds rotating around Venus, as captured by the ultraviolet imaging apparatus of the Akatsuki probe.
Something strange is happening in the clouds of Venus. Telescopes detected unusually high concentrations of phosphine - a smelly and flammable chemical usually associated with faeces, gas emissions and other microbial decay activities - in one of the layers of the atmosphere far from the surface of the burning planet.
The strangeness of this discovery is due to the fact that phosphine on planet Earth has always been linked to living organisms, either as a by-product of metabolic processes, or to technology used by humans, such as industrial vaporizers and methamphetamine laboratories. Despite the toxicity of phosphine to many living organisms, it was singled out for mention as a clear sign of the possibility of life on Venus. Because it is extremely difficult to form through normal geological or atmospheric processes.
Venus is like hell, as it is enveloped by clouds of sulfuric acid, and it is characterized by stifling surface pressure and temperatures high enough to dissolve lead, but the cloud layer in which phosphine is present is characterized in particular by its relatively moderate temperature, as it is flooded with sunlight and its air pressure Its temperature is similar to the atmospheric pressure and temperature on planet Earth. The scientific community will have to study these results carefully, but they seem to have renewed interest in exploring our closest planets.
"It's a really bewildering discovery because phosphine does not fit our perception of the kinds of chemicals that are supposed to be in the atmosphere of Venus," says Michael Wong, an astrophysicist at the University of Washington. Sanjay LeMay, a planetary scientist at the University of Wisconsin-Madison, agrees. "The bottom line is that we don't know what's going on," he says. (Neither Wong nor Sanjay was involved in this research effort).
Venus is the brightest object visible to the naked eye in the Earth's sky, after the sun and the moon. For thousands of years, tales have been told about this sparkling gem that appears close to sunrise and sunset. The luminosity of Venus piqued the interest of Jane Graves, a radio astronomer at Cardiff University in Wales. Graves is primarily focused on nascent and distant planetary systems, but this time she wanted to test her ability to recognize particles in worlds near our planet.
In 2017, Graves monitored Venus using the James Clerk Maxwell Telescope on Mount Mauna Kea in Hawaii, looking for patterns of vertical and parallel lines in the planet's spectrum that might indicate the presence of different chemicals. While monitoring, Graves noticed a streak associated with phosphine. The data indicated that the molecule was present at about 20 parts per billion in the planet's atmosphere, which is 1,000 to a million times more than its concentration on Earth. "I was dumbfounded," says Graves.
Phosphine is a relatively simple molecule. It contains one phosphorous atom and three hydrogen atoms. Phosphine is known to smell like garlic or rotten fish, but it is more likely to cause lung damage when it reaches concentrations that humans can smell. It should be noted that in the first episode of "Breaking Bad", Walter White's character is shown preparing phosphine gas to get rid of the two men in the gang who threaten him
But the preparation of phosphine was not as easy as we see on TV; Phosphorous and hydrogen are “repelled by one another,” says Clara Sousa-Silva, a specialist in molecular astrophysics at the Massachusetts Institute of Technology and co-author of a study on creating phosphine. “Hydrogen prefers to do other things, just as phosphorous prefers to bond with oxygen. But if we provide them with enough energy, they can bind together and settle in certain environments,” says Susa-Silva.
Jupiter and Saturn - which are two gas giants - are on the phosphine; Due to the hotness of their inner surface and hence the availability of the necessary energy for the formation of the molecule. The volatile atmosphere of Venus, known for its high concentration of greenhouse gases, is rich in chemicals that contain oxygen, such as carbon dioxide, which normally absorbs the phosphorous needed to form phosphine. So the existence of the molecule in any ratio, let alone the ratios that Graves observed, was a real mystery.
Susa-Silva - and her Twitter account @DrPhosphine - has devoted her career to studying phosphine and predicting how it would appear in the atmosphere of distant exoplanets. "I was looking at those strange worlds that are light-years away from us, including the super-terrestrial planets, the equatorial planets, the drainage planets, and all the time phosphine was here near us," Sousa-Silva says.
The researchers and co-workers made subsequent observations of Venus using the Atacama Large Millimeter / Sub Millimeter Array (ALMA) most effective in Chile last year, and repeated observations of phosphine in the atmosphere. Then they began to think about all the possible causes behind this strange presence of phosphine, which includes volcanic activity, lightning strikes, and even meteorite fission in the planet's atmosphere. "In my opinion, the best explanations we were able to come up with were substandard by a factor of 10,000," says Graves.
Naturally, there may be other mechanisms for phosphine formation that the team has not yet considered, but after exhausting all conceivable possibilities in search of abiotic explanations, the team did not find it inevitable to refer to another possibility in their research - which was published today in the journal Nature Astronomy - which is That the molecule may have been formed by the presence of life on Venus, as it is the case for its formation on Earth.
Life in the clouds Astrobiologists have long been fond of the rocky, dry planet Mars, whose environmental conditions are not much different from those of Earth. More recently, their fascination with potentially livable icy worlds outside the solar system has begun, such as Saturn's moon Enceladus, which has hot fizzes, and Jupiter's oceanic moon, Europe. Despite the obstacles surrounding Venus, it has also had its share of interest in scientists speculating about the idea of extraterrestrial life.
At a range of 50 to 60 kilometers above the surface of Venus, there is a layer of atmosphere whose pressure is equal to the pressure at sea level on planet Earth, and its temperature ranges between 0 and 50 degrees Celsius. Without sulfuric acid clouds in this layer, it would be considered "habitable". Even with the presence of sulfuric acid, there are organisms on planet Earth that can tolerate these extremely high acid levels in hot springs or other environments. This region with relatively mild conditions is precisely where the phosphine was found.
Since the 1960s, astronomers have also noted that the clouds of Venus do not reflect enough of the sun's ultraviolet rays It seems that something in the atmosphere absorbs this light only. This observation led late astrophysicists Harold Morowitz and Karl Sagan to hypothesize that living things hungry for the energy for photosynthesis might be the culprit.Meanwhile, other researchers have never stopped searching for alternative abiotic explanations. Recent evidence indicates that the planet is still geologically active. A model published earlier this year revealed that Venus had contained an ocean for nearly three billion years, and that it had only disappeared from a few hundred million years ago. It is possible that life arose on Venus when its conditions were more like Earth's, then became restricted to the atmosphere only due to the unbridled influence of greenhouse gases, which rendered the planet's surface uninhabitable.
"I have always thought it plausible that there was as much life in the clouds of Venus as it could be found beneath the surface of Mars," says David Grinspoon, an astrophysicist at the Institute of Planetary Sciences who was not involved in the study. Certainly so. "Nevertheless, there is an equally valid argument that Venus’s clouds are not as conducive to life as we know it. It is true that microbes float in the planet's atmosphere, but they do not spend their entire life cycle there; All of them must land on the planet's surface in the end, and conditions on the surface of Venus are completely unfavorable, which makes it an unsuitable place for life.The study area of Venus is 50 times drier than the Atacama Desert in Chile, which is the driest region on our planet. It is true that living organisms may have found their way to grow in aqueous environments marred by the effects of sulfuric acid, but the environmental conditions on Venus are completely opposite to this combination. It is a layer of clouds consisting mainly of sulfuric acid and just a little bit of water.
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