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The search for life in our solar system got much more exciting this week. On Monday, a team of scientists announced that their members had detected phosphine gas in the hot, caustic atmosphere of Venus. And that? The gas, which you would recognize by its fishy smell, is believed to be a by-product of life.
“We looked extensively at all known chemistry … and found nothing that could produce more than the tiniest amount of phosphine in Venus’ atmosphere,” says MIT planetary scientist Sara Seager, who was one of the co-authors of the discovery published in Nature astronomy, He says. That leaves us with two possibilities: the gas was created by life or by some chemical interaction that scientists don’t yet know about.
Seager is one of the leading dreamers and thinkers of astronomy, seeking life beyond our planet. She studies planets that orbit stars many light years away and thinks about how to detect life on them and others closer to home, like Venus.
You are also thinking creatively about the microscopic life forms that might survive there. This summer, before the phosphine announcement, she and her co-authors published a hypothetical and speculative sketch of what life might be like on Venus. The sight is beautiful: a living shower of microbes floating, cyclically, in the clouds, blooming and drying continuously for millions of years.
I wanted to hear more about this vision of life in a world so different from ours, so I called her.
This conversation has been edited for clarity and length.
Evidence of life on the neighboring planet
Brian Resnick
To get started: What is the essence of the discovery that you and the team announced this week?
Sara seager
We are not saying that we have found signs of life. We claim that we have a robust detection of phosphine gas in the atmosphere.
[After searching] all known chemistry (volcanoes, photochemistry, lightning) we found nothing that could produce more than the tiniest amount of phosphine in the atmosphere of Venus. So we are left with two possibilities. One is that there is some kind of unknown chemistry, which seems unlikely. And the other possibility is that there is some kind of life, which seems even more unlikely. So that’s where we are. It took me a long time to accept it.
Brian resnick
Well then it is highly unlikely. Has Venus been historically thought of as a place where life could exist in the solar system?
Sara seager
It has been marginal practically as long as it has been an issue. Carl Sagan first proposed that there could be life in [Venus’s] clouds. There is a small group [of scientists] who writes on this topic. Many people love it. It’s like a love in the closet because a lot of people are raving about it but either didn’t want to say it or never had a reason to say it.
Brian Resnick
What do you love about him?
Sara seager
I think it’s just the intrigue that there can be life so close to home.
[Venus is closer to Earth than Mars. It’s also the second-brightest object in our night sky, other than the moon.]
Why life should exist in the clouds of Venus, not on the surface
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Brian resnick
As I understand it, if life exists on Venus, would it not be on the planet’s surface, but in its sulfuric acid clouds?
Sara seager
It has always been the theory because the surface is too hot for complex molecules.
Brian resnick
What is too hot? What happens there?
Sara seager
Molecules break down. If you take a protein or an amino acid, or whatever, and put it on high heat, it breaks down into smaller fragments and atoms.
Brian Resnick
Why, then, is the atmosphere a better place to seek life?
Sara seager
It has the things that astrobiologists believe life needs. You need some kind of liquid. And there is liquid in the atmosphere, although it is liquid sulfuric acid.
Life needs a source of energy. So the sun definitely exists, at least as a source of energy. Life needs the right temperature. In the atmosphere, there is the right temperature. And life needs a changing environment to promote Darwinian evolution. So if you want to break it down like this, that’s why. For simplicity, it is primarily the argument from temperature. Temperature and liquid.
Brian Resnick
Do we know of any life forms on Earth that can exist in liquid sulfuric acid?
Sara seager
No we don’t.
Brian Resnick
What makes it seem possible for life to exist in sulfuric acid?
Sara seager
We just don’t know. I think your questions are basically the next decades of research.
Brian resnick
How can you even begin to imagine life in such a different world, a life that has to live in conditions that would be deadly to any life on Earth?
Sara seager
It has to be made up of different building blocks that our life is made of. Our building blocks, like proteins, amino acids, and DNA, would not survive in sulfuric acid. Or life must have found a way to have a protective layer, made of materials resistant to sulfuric acid.
The dance of life (potential) on Venus
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Brian Resnick
During the summer, you and your colleagues published an article speculating about what life would be like on Venus. She describes that she could basically dance in the atmosphere, alternating between an active phase up and an inactive phase down. I found it a bit beautiful. Can you describe how you came up with this?
Sara seager
I had to help plug a hole in the concept of life in the atmosphere. That’s where it came from. Life has to live inside the liquid droplets, to be protected from the outside.
But in these drops, where life lives, reproduces and metabolizes, the drops collide and grow.
Over time, like four months or a year or so, the droplets grow large enough that they begin to settle out of the atmosphere, like rain, but very slowly.
Then my colleagues told me that I had to find out how life could survive. If everything just rains, it could not stay in the atmosphere for billions of years or hundreds of millions of years.
Brian Resnick
How did you solve this?
Sara seager
Then I came up with this idea of the life cycle: when the drops fall, they evaporate and we are left with a dry life form, similar to a spore. That is not very massive; stops falling and is suspended in a layer of mist [lower down in the atmosphere]. And this layer of haze is known to exist under the clouds of Venus. It is very stable and long lasting. So the concept is that this layer of haze is populated by dry spores, which can stay there for days, weeks, months and years, eventually returning to the region that is the right temperature for life, where they can attract fluid, hydrate it. and start its life cycle again.
Brian Resnick
It is like a kind of living rain.
Sara seager
Right.
Brian resnick
Why wouldn’t the spore die suspended in that lower layer?
Sara seager
It’s quite hot there so some might die. And this is all just a hypothesis, so it’s not a proven theory or anything, but for this to work, some of them have to live. We have examples on Earth of dry spores that live a long time.
What would it mean to discover life on Venus
Brian resnick
Why is it important to do this kind of exercise, to be so speculative and to imagine life in a world seemingly so hostile to life?
Sara seager
If we think about it and can’t find any possible way for life to be in the atmosphere indefinitely, it would be bad news for life on Venus enthusiasts. Makes sense?
Brian resnick
Yes, if you cannot think of any hypotheses that will allow life to survive, it is difficult to make a case to go looking for it. Does the life you envision fit with the new discovery of phosphine gas?
Sara seager
Yes. Well, it was motivated by the phosphine work.
Brian Resnick
What would it mean to find life on Venus?
Sara seager
I think it would mean that if there is life there, it has to be very different from Earth and that we could show that it has a unique origin. It would simply give us the confidence that life can originate almost anywhere. And that would mean that our galaxy would be full of life. All planets around other stars. It just increases our thinking that there could be life everywhere.
Brian resnick
Are you talking about a second genesis of life that occurs separately on Venus? Or would we have to find out if there is a common origin of life in our solar system? Did that something sow life on both Earth and Venus?
Sara seager
We would have to figure it out.
How to find life on Venus, once and for all
Brian resnick
What are the next steps, ideally?
Sara seager
Our ideal next step would be to send a spacecraft or spacecraft, plural, to Venus, which could involve a probe that enters the atmosphere and measures gases that confirm phosphine, looks for other gases, looks for complex molecules that could indicate life and such. even looking for life itself.
Brian resnick
Is anyone working on that?
Sara seager
Rocket Lab had mentioned about a month ago that they planned to send a rocket to Venus. There are two NASA discovery class missions in a Phase A competition [meaning they’re just mission proposals and need to be greenlit]. if they are selected for launch, they will be able to leave. Russia and India plan to send something there. And I started running a privately funded study. It is not a mission. It is just a study of what would really be needed.
Brian Resnick
Can we answer this question: is there life on Venus, in our lives?
Sara seager
I think it can be answered in a human life.
Brian resnick
Is too much time and money spent finding life on Mars? Venus appears to be neglected in terms of large NASA missions.
Sara seager
Well, we don’t have infinite resources, unfortunately, but it sure would be nice to see more spent on Venus. We haven’t explored Venus for a long time. You would have to look up when was the last time America went to Venus. [It was the Magellan mission that launched in 1989.]
Brian resnick
What would you like the audience to think about and stop with on this topic?
Sara seager
Our solar system, our galaxy, our universe is full of mysteries. We would like to solve them, but some end up being unsolvable and simply leave us in limbo. So hopefully that won’t be the case here.
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