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Is there life on Venus? If there is, it would have to be unlike anything we’ve ever seen! New evidence means the possibility of life there is in question, but it could also mean a few other things.

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We can't say there's life on Venus. But now, we really can't say there's not life on Venus, either. Which is a 2020 plot twist nobody saw coming.

On September 14th, researchers from multiple universities published a paper in the journal Nature Astronomy, announcing that they'd found a lot of phosphine gas in Venus's atmosphere. And it got people talking. Because phosphine can be a biosignature.

In other words, if you can find enough of it, that could mean it's being made by life. But it could also mean a few other things. So, here's what we know, and how we'll get to the bottom of this.

Humans have been looking at Venus for millennia, and we've even sent spacecraft there. So it might seem surprising that nobody has ever noticed all this phosphine before. But that's because we weren't looking for it.

Looking for biosignatures normally requires heavy-duty telescopes. So no one had really tried searching for them on Venus until this study. The researchers haven't said a lot about why they chose to look for phosphine specifically, but they did!

And to do it, they used the James Clerk Maxwell Telescope in Hawai'i and the Atacama array in Chile. And they searched for the gas by studying sunlight as it bounced off Venus's surface and filtered through its atmosphere. Mostly, they were looking at one specific wavelength of light: the kind that phosphine absorbs.

The idea was that, if some of that light was missing, that would tell the team phosphine was in the atmosphere, and how much. And in the end, they found a bunch of it. Data from both telescopes showed the same dip in light, which corresponds to 20 molecules of phosphine per billion.

And I know that doesn't really sound like much, but even a few parts per billion was a surprise, because on Earth, phosphine is only made by industry and microbes, and it breaks down really fast. So the team started to search for possible sources on Venus. The most plausible one is that the phosphine is being made by abiotic processes, or things that aren't alive, like lightning or volcanoes.

Except these processes are hundreds of thousands, if not millions of times too slow to make even 20 phosphine molecules per billion. So, after what the authors called an “exhaustive study” of other processes, they concluded that they don't know where this gas is coming from. Maybe it's something abiotic we don't know about… or maybe it's life.

That's still a very big “maybe,” considering that we don't really know how life makes phosphine on Earth. But let's say that there is life on Venus. How would that even work?

I mean, Venus is notoriously hostile. The surface can reach 471 degrees Celsius, which is hot enough to melt lead. And the atmosphere isn't a whole lot more friendly.

It's full of carbon dioxide, and the clouds are sulfuric acid. Well, a few of the researchers on last week's paper also published another paper in August, in the journal Astrobiology. And it's got some ideas.

In it, the team suggested that life on Venus would be microbial. And instead of living on the surface, it would thrive in the temperate zone. That zone covers the middle and lower regions of Venus' clouds, and it's not the worst place to live.

The pressure is similar to Earth's, and the temperature can be around 30 degrees Celsius. I mean, the clouds are still sulfuric acid, but it's as habitable as you're going to get. It's also where the team detected all this phosphine in last Monday's paper.

So, based on what they know about Venus and about life on Earth, the researchers believe it's possible that small, microbe-like particles could float within liquid droplets in these clouds. But, there are also two problems here:. First, droplets don't stay the same size forever.

And as they combined with other droplets, they would eventually get heavier and fall toward the ground. Then, as they fell out of the temperate zone, they'd heat up, and the sulfuric acid would break down. But the authors of this paper actually had a solution for that one.

They proposed that the microbes would become dehydrated, spore-like things, floating around in the lower atmosphere. Then, eventually, waves in Venus's atmosphere would sweep the spores back up to the temperate zone, where they'd be rehydrated and continue on with their lives. But then there's the other problem.

Venus's clouds are more than a hundred billion times as acidic as anything on Earth, and would quickly destroy everything from lipids to proteins to carbohydrates, which is basically what life on Earth is made of. So if there's life on Venus, it'd have to be unlike anything we've ever seen. That's not out of the question.

But again, this is all hypothetical at this point. Right now, it's more likely that we just don't know enough about Venus's geology, and that something abiotic is responsible for all of this. To know if there's life on Venus, we'll need to learn more about the planet itself, and eventually send a satellite to take measurements.

Which could be a few years. But if nothing else, we are going to try to confirm these data about phosphine really soon. Right now, the European and Japanese space agencies are flying a mission to Mercury called BepiColombo.

And coincidentally, it'll swing by Venus next month and will try to check for phosphine as it flies by. But beyond that… We'll have to be patient. And hey: Even if there's no alien life on Venus, this discovery brings us closer to understanding a planet we know surprisingly little about.

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