An international team of scientists that included members from MIT may have found signs of life floating in the clouds of the planet Venus.
The scientists detected phosphine in the clouds, an odoriferous, poisonous gas that they believe may have been produced by life.
The astronomers, led by Jane Greaves of Cardiff University in Wales, published their work in the journal Nature Astronomy.
“It is unbelievably important, and it is unbelievably exciting. Everything about this is completely unexpected,” Janusz Petkowski, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences, who was one of the paper’s coauthors, said Monday in an interview.
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The scientists detected phosphine using the James Clerk Maxwell Telescope in Hawaii, and the Atacama Large Millimeter Array observatory in Chile. Massachusetts Institute of Technology scientists performed an exhaustive analysis to see whether anything else could have produced the phosphine. They could find no other explanation than the possible presence of life.
“It’s very hard to prove a negative,” Clara Sousa-Silva, an MIT colleague of Petkowski’s and also a coauthor of the paper, said in a statement from the university. “Now, astronomers will think of all the ways to justify phosphine without life, and I welcome that. Please do, because we are at the end of our possibilities to show abiotic processes that can make phosphine.”
“This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets,” Petkowski said in the statement.
The phosphine, which is made with one phosphorus atom and three hydrogen atoms, "could originate from unknown photochemistry or geochemistry, or, by analogy with biological production of [phosphine] on Earth, from the presence of life,” the study said.
The finding about Venus comes as interest has been focused in recent years on the possibility of life on Mars.
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Named for the Roman goddess of love and beauty, Venus, the second planet from the sun, is similar in size and structure to Earth, but its thick atmosphere traps heat, making it the hottest planet in the solar system, with surface temperatures high enough to melt lead.
While the surface is inhospitable, there is a narrow band in the planet’s atmosphere around 30 to 37 miles above the surface where temperatures range from 30 to 200 degrees Fahrenheit, the university said.
Scientists had speculated that that was the only place where life could survive. And that’s where the phosphine was detected, the university said.
The idea of life in the clouds of Venus had been raised decades ago by astronomer Carl Sagan, Petkowski said.
Sousa-Silva said biomolecules had been found in the planet’s atmosphere before, but those molecules were "also associated with a thousand things other than life. The reason phosphine is special is, without life it is very difficult to make phosphine on rocky planets. Earth has been the only terrestrial planet where we have found phosphine, because there is life here. Until now.”
Sousa-Silva speculated that life could have taken to the sky on Venus in the unimaginably distant past.
“A long time ago, Venus is thought to have oceans, and was probably habitable like Earth,” she said. “As Venus became less hospitable, life would have had to adapt, and they could now be in this narrow envelope of the atmosphere where they can still survive. This could show that even a planet at the edge of the habitable zone could have an atmosphere with a local aerial habitable envelope.”
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Sarah Stewart Johnson, a planetary scientist and head of the Johnson Biosignatures Lab at Georgetown University who was not involved in the work, said, “There’s been a lot of buzz about phosphine as a biosignature gas for exoplanets recently,” referring to the search for life on worlds that orbit other stars. “How cool to find it on Venus.”
She added: “Venus has been ignored by NASA for so long. It’s really a shame.”
David Grinspoon of the Planetary Science Institute in Tucson, Ariz., who was not part of the work but has long promoted the possibility of life in Venus’s clouds, said, “That is pretty damn exciting!”
The work needs to be followed up, he said, “but this could be the first observation we’ve made which reveals an alien biosphere and, what do you know, it’s on the closest planet to home in the entire cosmos.”
“The finding itself is astonishing,” said Paul Byrne, a planetary scientist at North Carolina State University in Raleigh who was not involved in the research. He said that although he was “skeptical of it being life, I don’t have a better explanation for what it is.”
Petkowski said in the interview that scientists would welcome a mission to Venus to check out their hypothesis.
“Eventually, if we would like to really confirm or find life or prove life . . . we could go there and collect the cloud droplets and see what is inside those droplets,” he said. “If something is swimming inside those cloud droplets, then there you go, this is your proof.”
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The study’s coauthors also included other researchers from MIT and Cardiff, as well as from the University of Manchester, Cambridge University, MRC Laboratory of Molecular Biology, Kyoto Sangyo University, Imperial College, the Royal Observatory Greenwich, the Open University, and the East Asian Observatory, the university said.
Material from Globe wire services was used in this report.
Martin Finucane can be reached at martin.finucane@globe.com.