In Depth

Life on Venus? What we know so far

Astronomers announce ‘mind-boggling’ discovery of ‘biosignature’ gas phosphine in clouds above the planet

Traces of a highly toxic gas released by microbes in oxygen-starved environments has been detected in the atmosphere above Venus, astronomers have revealed.

The international team announced the discovery in a newly published paper in the journal Nature, but have “failed to identify a process other than life that could account for its presence”, The Guardian reports.

The findings have “shocked the astronomical community”, adds The Times. So could there really be life on Venus?

What did the team find?

According to current theories about the geological and atmospheric evolution of the planets of the Solar System, Venus was a temperate planet with an ocean - much like Earth - for around two billion years.

However, for the past 600 million years or so, Venus has experienced a runaway greenhouse effect triggered by the planet’s dense carbon dioxide atmosphere, with temperatures routinely hovering around 450C - an unsustainable temperature for any water or life as we know it.

Further up at cloud level, however, the temperatures are “much more mild” and could theoretically sustain life, Reuters reports.

The clouds are comprised mostly of sulphuric acid, “which is catastrophic for the cellular structures that make up living organisms on Earth”, says the BBC.

But the new discovery of the phosphine, about 30 miles above the surface of Venus, has fuelled theories that other forms of life could be living in the planet’s clouds.

Phosphine is a molecule consisting of hydrogen and phosphorus atoms that is produced on Earth by microbial life forms that live in oxygen-free environments.

The gas has previously been detected in the clouds of Jupiter and Saturn, both of which are rich in hydrogen, and is produced on Earth by “microbes living in the guts of animals like penguins, or in oxygen-poor environments such as swamps”, the BBC says.

“As such, it is thought to be an excellent ‘biosignature’, or indication of life,” adds The Independent

And that makes the Venus findings “mind-boggling”, says Sara Seager, a planetary scientist from Massachusetts Institute of Technology who worked on the study. 

So what does it all mean?

Although the latest discovery is “not a direct observation of life on another planet”, the “sheer quantity of phosphine on Venus cannot be explained through any known process, leading researchers to suggest that it is a sign of alien life in our solar system”, says The Independent.

As The Times explains, phosphine is “ephemeral, rapidly reacting and disappearing”, so “to be present, it must be replenished”. Yet the research team, led by Cardiff University astronomer Professor Jane Greaves, say the gas is not made by any known chemical or geological process on Venus.

“It’s completely startling to say life could survive surrounded by so much sulphuric acid,” said Greaves. “But all the geological and photochemical routes we can think of are far too underproductive to make the phosphine we see.”

All the same, “the conditions on Venus are so deeply unpleasant that many scientists believe the planet is dead”, reports The Guardian. Instead, experts suspect the phosphine detected “arises from more mundane processes”.

Charles Cockell, an astrobiologist at the University of Edinburgh, told the newspaper that rather than hinting at life on Venus, the new research findings raise questions about phosphine as a “biomarker”.

“A biological explanation should always be the explanation of last resort and there are good reasons to think the Venusian clouds are dead,” he said. “The concentrations of sulphuric acid in those clouds are more extreme than any known habitat on Earth.”

Study co-author Emily Drabek-Maunder, an astrophysicist from the Royal Observatory Greenwich, agrees that the phosphine may be “produced by some sort of chemical or geological process that no one knows about”.

But she suggests that “there could be a biological reason”, adding: “If life formed independently on Venus then life is probably a lot more common than we thought.”

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