Venus: Possible evidence of life in the clouds?

Guest “The truth is out there” by David Middleton

Phosphine gas found in Venus’ atmosphere may be ‘a possible sign of life’
Astronomers detected signs of a smelly, toxic gas that microbes can make in the planet’s clouds

By Lisa Grossman


Venus’ clouds appear to contain a smelly, toxic gas that could be produced by bacteria, a new study suggests.

Chemical signs of the gas phosphine have been spotted in observations of the Venusian atmosphere, researchers report September 14 in Nature Astronomy. Examining the atmosphere in millimeter wavelengths of light showed that the planet’s clouds appear to contain up to 20 parts per billion of phosphine — enough that something must be actively producing it, the researchers say. 

If the discovery holds up, and if no other explanations for the gas are found, then the hellish planet next door could be the first to yield signs of extraterrestrial life — though those are very big ifs.

“We’re not saying it’s life,” says astronomer Jane Greaves of Cardiff University in Wales. “We’re saying it’s a possible sign of life.”


“Fifty kilometers above the surface of Venus, the conditions are what you would find if you walk out of your door right now,” at least in terms of atmospheric pressure and temperature, says planetary scientist Sanjay Limaye of the University of Wisconsin–Madison, who was not involved in the new study. The chemistry is alien, but “that’s a hospitable environment for life.”

Previous work led by astrochemist Clara Sousa-Silva at MIT suggested that phosphine could be a promising biosignature, a chemical signature of life that can be detected in the atmospheres of other planets using Earth-based or space telescopes.

On Earth, phosphine is associated with microbes or industrial activity — although that doesn’t mean it’s pleasant. “It’s a horrific molecule. It’s terrifying,” Sousa-Silva says. 


Science News

The full paper (Greaves et al., 2020) is available. Here’s the abstract:


Measurements of trace gases in planetary atmospheres help us explore chemical conditions different to those on Earth. Our nearest neighbour, Venus, has cloud decks that are temperate but hyperacidic. Here we report the apparent presence of phosphine (PH3) gas in Venus’s atmosphere, where any phosphorus should be in oxidized forms. Single-line millimetre-waveband spectral detections (quality up to ~15σ) from the JCMT and ALMA telescopes have no other plausible identification. Atmospheric PH3 at ~20 ppb abundance is inferred. The presence of PH3 is unexplained after exhaustive study of steady-state chemistry and photochemical pathways, with no currently known abiotic production routes in Venus’s atmosphere, clouds, surface and subsurface, or from lightning, volcanic or meteoritic delivery. PH3 could originate from unknown photochemistry or geochemistry, or, by analogy with biological production of PH3 on Earth, from the presence of life. Other PH3 spectral features should be sought, while in situ cloud and surface sampling could examine sources of this gas.

Greaves et al., 2020

Evidence of biological processes in Venus’ atmosphere? Maybe. However, “unknown photochemistry or geochemistry” is probably more likely than “biological production” because we don’t even really know what the unknowns are. Evidence of polycyclic aromatic hydrocarbons (PAHs) in Titan’s atmosphere isn’t evidence of “incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco or charbroiled meat” on Titan

In what I think was a spoof, Tucker Carlson interviewed UFO “expert” Nick Pope abut this discovery:

I have no idea how Tucker maintained s straight face through that interview… I know I couldn’t have. Oh… don’t pay any attention to: “See David Middleton’s other Tweets”… There’s not much to see. I almost never use Twitter. It was the only way I could figure out how to share the video.


Greaves, J.S., Richards, A.M.S., Bains, W. et al. Phosphine gas in the cloud decks of Venus. Nat Astron (2020).

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