EVIDENCE FOR ALIEN LIFE? ‘It’s basically either not a big deal, or we just found Venusians and that’s incredible’ An extraordinary discovery in the atmosphere of

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There may be life swirling around in the Venusian atmosphere

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 (Nature Astronomy, DOI: 10.1038/s41550-020-1174-4). “It’s basically either not a big deal, or we just found

“It’s basically either not a big deal, or we just found Venusians and that’s incredible”

Venusians and that’s incredible,” says Sousa-Silva. “The fact that M A

E it’s even a possibility is really T

T C E

J breathtaking to me.” O R P

I The idea of life floating about K U S

T in the Venusian clouds isn’t A K A / entirely out of the blue. The S A S I

/ surface may be crushingly A X A J dense and hot, but among the clouds it is relatively Astrobiology temperate. “For decades, people have argued that Venus may be habitable,” says Paul Byrne at Signs of ? North Carolina State University. “Before it was just a conjecture, a place where biology could The atmosphere of our sister contains a gas that in theory be possible, but now hints at an extraordinary discovery, says Leah Crane we have this phosphine.” Greaves and her colleagues THE clouds of Venus may contain Clerk Maxwell Telescope in Hawaii The only way phosphine is are now working on confirming life. Some 50 to 60 kilometres and the Atacama Large Millimeter/ made on Earth is in laboratories the observations of phosphine above the planet’s surface, there submillimeter Array in Chile. or by microbes. It also exists with far more detailed are small quantities of phosphine The data from both telescopes deep inside giant , but measurements, but to be sure gas, a substance that is present showed signs of phosphine gas its formation requires conditions where it is coming from we will in Earth’s atmosphere because in the Venusian clouds, which that don’t exist on Venus. probably have to send a spacecraft it is produced by microbes was completely unexpected. The researchers tested a variety to Venus to take a closer look. and by human technological “Phosphine in that of ways to produce phosphine “You want to get into the processes. There are no known environment is a weird thing on Venus, from atmospheric atmosphere and sample it to non-biological mechanisms to observe. It doesn’t belong chemistry to volcanism to see what’s there,” says Byrne. for making this amount of gas there,” says David Grinspoon delivery by meteorite, but they If those samples have life in on Venus, so it may be being at the Planetary Science Institute couldn’t account for the amount them, even if it is tiny microbes, produced by alien microbes. in Arizona, who wasn’t involved of phosphine observed in the data. the planet next door could Jane Greaves at Cardiff in this research. “It would get “We thought of every process upend our ideas about what University, UK, led a team destroyed – there has to be a that could produce phosphine, life can be and how it arises. ❚ of astronomers who looked source.” Somehow, the phosphine and none of them produced Still have questions? See our at Venus using the James has to be continuously replenished. phosphine in anywhere near readers’ Q&A on page 8

19 September 2020 | New Scientist | 7 News

Q&A The Venusian enigma This week’s news from Venus left many of our readers with questions. Here our resident space expert, Leah Crane, tries to answer some of them

A TEAM of researchers has used What capabilities would a two of the biggest telescopes on spacecraft need to investigate Earth, including the ALMA possible life on Venus? telescope in Chile (pictured right), You would want to be able to to find signs of phosphine gas sample the atmosphere and on Venus – a compound that chemically analyse it. A spacecraft is produced on our planet only would need to be able to look by industrial processes and for life, which can show itself in microbes – and raised many patterns of materials consumed questions about whether we and released, but also to examine have just found alien life. the atmosphere more generally in case the phosphine isn’t How hot is Venus? Would biologically produced. any life there burn up? There are a lot of different Could we use an atmospheric environments on Venus because balloon to search for signs of of its thick atmosphere. The surface life on Venus? is absolutely miserable, with The hot, dense atmosphere N I temperatures reaching 470°C and L makes it hard to send spacecraft A M

. pressures 90 times that at sea level C to Venus, but several have made / O S on Earth. But it is pretty temperate E it down to the surface before where the phosphine was found, they burned up. There have at 50 to 60 kilometres above is produced by microbes, so you bears) aren’t known to produce been a couple of balloons sent ground level, so the atmosphere might expect microbes to be able phosphine, so if there is life on to Venus. It isn’t impossible, it is could be conducive to life. to make it on Venus too. If there is Venus it is probably something else. just a tough engineering problem. life there, it could be fairly simple. Why would the phosphine Would this be an indication Is this a significant enough gas stay at this altitude? Could it be that an organism that there was life on the surface find that NASA might decide The clouds of Venus aren’t shifting made this gas in the past and at one point? to focus on searching Venus and ephemeral like Earth’s clouds. is now extinct? It isn’t an indication that there is for life, rather than ? They are thick, their motions are The exciting thing is that this life on the surface now, but if there is NASA has been very focused on driven by convection and the gas isn’t really an option. The life in the atmosphere now, it could Mars for a while, but we are at a could just be floating around like researchers calculated that the have interesting consequences for point now where there aren’t many plankton in Earth’s ocean. lifetime of phosphine on Venus more planned Mars missions, aside should be less than 1000 years from still-very-theoretical crewed Do we know that this phosphine before it is destroyed, so 50-60km missions. While this news alone gas cannot be produced by anything something must be continually The altitude at which researchers probably isn’t enough to change other than biological processes? replenishing it for it to exist detected phosphine gas on Venus NASA’s course, it may be time It is impossible to prove a negative, in the concentrations we see. for something new. so unless we can show definitively If the organisms that may have our understanding of what may have that this phosphine was produced produced it are now extinct, they been on the surface back when it Do we have the capability to by life, there will always be a must have been around until pretty was – maybe – not so hot there. detect this quantity of phosphine chance that it was produced by recently. Given planetary timescales, on exoplanets – planets beyond a non-biological chemical process. it would be shockingly unlucky for Could the phosphine have come the solar system? But the team tested all the processes them to have died out just as we from microbes carried by the This amount of phosphine – about we know that could happen on became capable of finding them. Soviet spacecraft, which 20 parts per billion – is right on Venus, and none made enough visited Venus in the 1970s? the edge of what is detectable on gas to account for the amount Any chance it could be tardigrades That isn’t likely. The researchers planets outside the solar system. they have detected. in Venus’s atmosphere? found a large amount of phosphine, That means we probably can’t spot it Although they can endure extreme and the Venera landers were with any confidence at the moment, How big would an organism have temperatures, the microscopic, pretty small, so it is unlikely they but if we did find it on an exoplanet to be to create what was found? eight-legged Earth animals called carried enough microbes to seed it would be extremely exciting as Not big at all. On Earth, phosphine tardigrades (also known as water this much of the gas. a potential indicator of life. ❚

8 | New Scientist | 19 September 2020