Astronomers Find Possible Signs of Life in Venus Atmosphere

Astronomers have found a potential signal of life high in the atmosphere of our nearest neighboring planet, Venus. They caution they aren't certain yet, calling it hints of bizarre microbes living in the sulfuric-acid-laden clouds of the hothouse planet.

Two telescopes in Hawaii and Chile spotted in those thick Venutian clouds the chemical signature of phosphine, a noxious gas that on Earth only is associated with life, according to a study in Monday's journal Nature Astronomy.

Study authors and several outside experts say this is far from the first ever proof of life on another planet, but they can't quite find a good explanation, chemical or geological, that doesn't involve something alive.

And they agree it doesn't satisfy the stringent requirement established by the late Carl Sagan of "extraordinary claims require extraordinary evidence."

"It's a hint of a possibility of biology in the clouds of Venus," said study co-author David L. Clements, an Imperial College of London astrophysicist. "It's not a smoking gun. It's not even gunshot residue on the hands of your prime suspect, but there is a distinct whiff of cordite in the air which may be suggesting something."

As astronomers plan for future searches for life on planets outside our solar system, a major method is to look for chemical signatures that can only be made biological processes, called biosignatures. After three astronomers met in a bar in Hawaii they decided to aim that technique at the closest planet to Earth: Venus. And they looked for the obscure phosphine, which is three hydrogen atoms and a phosphorous atom.

On Earth, there are only two ways phosphine can be formed, study authors said. One is in an industrial process created by people, which included use as a chemical warfare agent in World War I, and the other as part of some kind of poorly understood function in animals and microbes.

Study co-author Sara Seager, an MIT planetary scientist, said the team of researchers "exhaustively went through every possibility and ruled all of them out: volcanoes, lightning strikes, small meteorites falling into the atmosphere. We worked all the known chemistry possible that might occur in Venus's atmosphere, on the surface and the subsurface. Not a single process we looked at could produce phosphine in high enough quantities to explain our team's findings."

"So we are left with two remote possibilities. One is that there's some unknown chemistry, some chemistry we don't know about. The second more intriguing possibility is that there might be some kind of life-form in the Venus atmosphere that is producing the phosphine that we have detected," Seager added.

Seager, Clements and colleagues have come up with a potential scenario for how life could exist on the inhospitable planet where temperatures on the surface are around 800 degrees (425 degrees Celsius) with no water of any form on the ground.

Seager said all the action may be 30 miles (50 kilometers) above the ground in the thick carbon-dioxide layer cloud deck. It's actually room temperature or slightly warmer and has the same atmospheric pressure on Earth, but of course you couldn't breathe it, Clements said. Adding to that there are droplets with tiny amounts of water but mostly sulfuric acid that is a billion times more acidic than what's found on Earth.

The phosphine could be coming from some kind of microbes, single cell life most likely, inside those sulfuric acid droplets living their entire lifetimes in the clouds, Seager and Clements said. When the droplets fall, the potential life likely dries out and could then get picked up in another drop and reanimate, they said.

If there is life there, it could stay in the atmosphere for millions of years this way, Seager said.

Life is definitely a possibility, but this isn't enough to say it's a probability yet, said several outside scientists contacted by The Associated Press.

One of the first scientists to suggest life was possible on Venus was the famed astronomer Sagan in 1967. Planetary Science Institute astrobiologist David Grinspoon is one of the biggest promoters of the theory, writing a 1997 book on it. He called the finding "a legitimate biosignature, a legitimate hint that there could be something on Venus."

NASA already is looking at two possible Venus missions, but hasn't made a decision yet. One of them, called DAVINCI+, would go into the Venutian atmosphere as early as 2026.

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