Traces of a rare molecule known as phosphine have been found in the hellish, heavily acidic atmosphere of Venus, astronomers announced Monday — providing a tantalizing clue about the possibility of life. Phosphine molecules found on Earth are primarily a result of human industry or the actions of microbes that thrive in oxygen-free environments.
The researchers are not claiming life has been detected on the second planet from the sun. But the observations suggest at least the possibility of microbial activity in the upper layers of Venus’ atmosphere, well away from the planet’s inhospitable surface.
“We have detected a rare gas called phosphine in the atmosphere of our neighbor planet Venus,” said Jane Greaves, a professor at Cardiff University in the United Kingdom and lead author of a report published in Nature Astronomy. “And the reason for our excitement is that phosphine gas on Earth is made by microorganisms that live in oxygen-free environments. And so there is a chance that we have detected some kind of living organism in the clouds of Venus.”
Phosphine is to Venus as methane is to Mars? 20 parts-per-million of phosphine have been detected in the temperate clouds of Venus, and its source is not evident.
“The surface conditions there today are really hostile, the temperature is enough to melt our landers,” Greaves said. “But it’s thought that much earlier in Venus’ history the surface was much cooler and wetter and life possibly could have originated.
“In order to make this quite extraordinary claim that there might be life there, we really have to rule everything out, and that’s why we’re very cautious saying we’re not claiming there’s life, but claiming there’s something that is really unknown and it might be life,” said team member William Bains, a researcher at MIT.
Sara Seeger, a fellow MIT scientist who studies exoplanet atmospheres, agreed, saying “we are not claiming we have found life on Venus.”
“We are claiming the confident detection of phosphine gas whose existence is a mystery,” she said. “Phosphine can be produced by some (non-biological) processes on Venus, but only in such incredibly tiny amounts it’s not enough to explain our observation. So we’re left with this other exciting, enticing possibility: that perhaps there is some kind of life in Venus’ clouds.”
Mars has long been considered the best candidate in the solar system beyond Earth to have hosted microbial life in the distant past or even in the present, as suggested by background levels of methane. NASA, the European Space Agency, China, India, Russia and United Arab Emirates are all pursuing exploration of the red planet in one form or another.
NASA also is planning a flagship mission to study the moons of Jupiter. Scientists believe one of the planet’s largest and best-known moons, Europa, heated by tidal stresses and gravitational interactions with other moons, harbors a salty, possibly habitable ocean beneath its icy crust. Other frozen moons in the outer solar system, possible “water worlds,” are also candidates for study.
But Venus is the victim of a runaway greenhouse effect in which thick clouds in a mostly carbon dioxide atmosphere trap sunlight, producing temperatures at the surface that soar to nearly 900 degrees, hot enough to melt lead.
In the planet’s upper atmosphere, however, temperatures are much more hospitable. Despite the acidic nature of the clouds, scientists have speculated it may be possible for alien microbes to exist.