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鈥檚 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聽astronomers who looked at聽Venus using the James Clerk聽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.
鈥淧hosphine in that environment is a weird thing to聽observe. It doesn鈥檛 belong there,鈥� says David Grinspoon at聽the Planetary Science Institute in Arizona, who wasn鈥檛聽involved聽in this research. 鈥淚t聽would get destroyed 鈥� there has to be a source.鈥� 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鈥檛 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鈥檛 account for the amount of phosphine observed in the data.
鈥淲e thought of every process that could produce phosphine, and none of them produced phosphine in anywhere near the amounts that we found it,鈥� says team member Clara Sousa-Silva at the Massachusetts Institute of Technology. 鈥淲e鈥檝e exhausted the possibilities.鈥�
Only two scenarios remain: either there is something going on in Venus鈥檚 clouds that we don鈥檛 understand, or whatever is producing all that phosphine is alive.
鈥淚t鈥檚 basically either not a聽big聽deal, or we just found Venusians and that鈥檚 incredible,鈥� says Sousa-Silva. 鈥淭he fact that聽it鈥檚 even a possibility is really breathtaking to me.鈥�
The idea of life floating about in the Venusian clouds isn鈥檛 entirely out of the blue. The surface may be crushingly dense and hot, but among the clouds it is relatively temperate. 鈥淔or decades, people have argued that Venus may be habitable,鈥� says Paul Byrne at North Carolina State University. 鈥淏efore it was just a conjecture, a聽place where biology could in聽theory be possible, but now we have this phosphine.鈥�
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聽spacecraft to Venus to聽take a closer look.
鈥淵ou want to get into the atmosphere and sample it to see聽what鈥檚 there,鈥� 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聽can be and how it arises.
Nature Astronomy
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