The clouds of Venus may contain life. Some 50 to 60 kilometres above the surface, there are small quantities of phosphine gas, a substance that is present in Earth’s atmosphere because it is produced by microbes and by human technological processes. There are no known non-biological mechanisms of making the gas on Venus, so it may be being produced by alien microbes.
Jane Greaves at Cardiff University, UK, led a team of astronomers who looked at Venus using the James Clerk Maxwell Telescope in Hawaii and the Atacama Large Millimeter/submillimeter Array in Chile. The data from both telescopes showed signs of phosphine gas in the Venusian clouds, which was completely unexpected.
“Phosphine in that environment is a weird thing to observe. It doesn’t belong there,” says David Grinspoon at the Planetary Science Institute in Arizona, who wasn’t involved in this research. “It would get destroyed – there has to be a source.” Somehow, the phosphine has to be continuously replenished.
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The only way phosphine is made on Earth is in laboratories or by microbes. It also exists deep inside giant planets, but its formation requires conditions that don’t exist on Venus.
The researchers tested a variety of ways to produce phosphine on Venus, from atmospheric chemistry to volcanism to delivery by meteorite, but they couldn’t account for the amount of phosphine observed in the data.
“We thought of every process that could produce phosphine, and none of them produced phosphine in anywhere near the amounts that we found it,” says team member Clara Sousa-Silva at the Massachusetts Institute of Technology. “We’ve exhausted the possibilities.”
Only two scenarios remain: either there is something going on in Venus’s clouds that we don’t understand, or whatever is producing all that phosphine is alive.
“It’s basically either not a big deal, or we just found Venusians and that’s incredible,” says Sousa-Silva. “The fact that it’s even a possibility is really breathtaking to me.”
The idea of life floating about in the Venusian clouds isn’t entirely out of the blue. The surface may be crushingly dense and hot, but among the clouds it is relatively temperate. “For decades, people have argued that Venus may be habitable,” says Paul Byrne at North Carolina State University. “Before it was just a conjecture, a place where biology could in theory be possible, but now we have this phosphine.”
Greaves and her colleagues are now working on confirming the observations of phosphine with far more detailed measurements, but to be sure where it is coming from we will probably have to send a spacecraft to Venus to take a closer look.
“You want to get into the atmosphere and sample it to see what’s there,” says Byrne.
If those samples have life in them, even if it is tiny microbes, the planet next door could upend our ideas about what life can be and how it arises.
Nature Astronomy
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