“I like to think someone’s out there waiting for us”: Meet the astrophysicist looking for alien life in the clouds of Venus

MIT professor Sara Seager has been chasing aliens for most of her adult life. In 2020, Seager was an adviser on the UK team of astronomers that discovered phosphine—a gas produced by living things—on Venus, which became a scientific flashpoint. Now, she’s leading the first privately funded mission to Venus, hoping the planet’s dense, acidic clouds harbour life. We spoke to Seager about her early days stargazing in Toronto, her upcoming Rocket Lab mission in 2026 and why Venus—long ignored in the red shadow of Mars—may be the key to finding alien life.

Let’s start with the basics. How do you describe what you do? You can laugh at this, but I see myself as the big boss. It’s my mission to find life outside of Earth. In addition to my research on exoplanets—planets outside of our solar system—I lead the Venus Morning Star Missions, which send astrobiology instruments to Venus. And professionally, I’m a professor of planetary science, physics and aerospace engineering. My interests overlap, and that makes me quite curious. If I had to have one word to describe myself, I’d say I’m an explorer.

You currently run your own lab at MIT, but you grew up in Toronto. What was your upbringing here like? I grew up in the South Annex, which wasn’t a nice place in the early ’80s. My parents were divorced, and my dad lived in Markham, so I spent time there as well. I went to Huron Public School and Jarvis Collegiate Institute, which was known for its science program.

My dad had a pretty eccentric view of the world. He believed in reincarnation, psychics and investigating what’s beyond the surface. He raised me to think big, and that’s what’s made me a great scientist. I’m open to unfathomable ideas, but I have the tools to sort fact from fiction. My dad had been a doctor before becoming a hair transplant specialist, and he wanted me to be a dermatologist, not an astronomer. But it all came together. I did my bachelor’s in math and physics at U of T, and I have wonderful memories of working through complex quantum mechanics and physics classes there. In June of 2023, they awarded me an honorary PhD.

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Was discovering life in space always the dream during those U of T days? Not exactly, but one of my first memories is looking at the moon on a camping trip to Bon Echo Provincial Park. When I stepped out of the tent, I looked up and saw so many stars. It was shocking. My dad was a member of the Royal Astronomical Society of Canada, an amateur astronomy organization. They throw campout star parties, and at some point I saw the moon through their telescope. I owe a lot to them. I joined the RASC later in life and met my second husband there. Now I’m their honorary president.

The society must be proud. Well, most of the members don’t know they have an honorary president, so there’s that.

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Let’s get to space. What’s the deal with Venus? Venus is a super interesting planet. I always liken the terrestrial planets—Earth, Mars and Venus—to siblings. Mars gets all the attention. We’ve sent missions there over and over, but Venus has been ignored for about four decades.

What changed? About five years ago, I was connected with Jane Greaves, an astronomer at Cardiff University in the UK. Their team was looking for signs of life on Venus, and I was asked to advise on their data. We discovered signs of phosphine on the planet, a gas that on Earth is made only by organisms. Even though I was only peripherally involved at the time, the discovery showed me what an interesting planet Venus might be—like the quiet sibling with something to say if they’d only cough up their secrets.

How did it feel to find possible evidence of life? I was in disbelief. I didn’t have a sudden moment of joy, but over time the reality set in. In science, it pays to be naïve and to balance optimism with pragmatism. The data was a bit sketchy, so my hopes were low, but after deep investigation, the pieces came together. I remember saying to my mentor, “Wow, this Venus mission could really work.” But, after our public announcement, we were attacked on every level by other scientists.

Why was it so controversial? There were three big concerns. First, the signal was very faint. Some wondered if it was actually phosphine. And if it was, perhaps it could be produced by something other than life—Venusian volcanoes, for instance. We wrote a 100-page report showing that no one possibility could explain the tiny amount we’d detected. But, still, there might be some unknown chemistry we haven’t discovered yet. Science can take years to sort these things out. For me, though, it was a career crisis. There I was, looking for life on other solar systems. If there was this much debate over something happening next door, how would people ever believe me if I found something light years away?

How did you keep going? Our findings opened a door that helped secure seed funding and gather a team. We held planning meetings—sometimes with up to 80 people—and at one of them, someone from Rocket Lab in California joined. You never know who’s paying attention in those big Zooms. Later, they reached out and said, “We’ve wanted to send a mission to Venus. You have the science; we have the rocket.” Just like that, the first largely privately funded Venus mission was born.

What’s the landscape like on Venus? It’s bad. It’s about 425 degrees on the surface, far too hot for life. Some of the former Soviet Union probes that landed lasted only about an hour before breaking down beyond communication. But, just like when you climb a mountain on Earth, the air gets colder with altitude. Fifty kilometres above the surface of Venus, it’s the same temperature and the same pressure as Earth. And here on Earth, we have life in the clouds, in the form of bacteria that get swept up into the sky. Half a century ago, Carl Sagan first proposed the idea that there might be little primitive bacteria in the clouds of Venus. The problem is, Venus’s clouds aren’t made of water like ours, they’re made of concentrated sulphuric acid—a substance that would kill any Earth life. It burns holes in your clothes and your skin.

Could anything survive in an acid cloud? We’re conducting lab work here on Earth where we’re putting molecules like amino acids into concentrated sulphuric acid to see what survives. Most are surprisingly stable, and we’re even trying to build a DNA-like molecule that could store information in harsh conditions. If we can show that something like that is possible, it would open up more possibilities of life, both on Venus and elsewhere.

What’s this little probe you’re sending to Venus next year going to do? Our team, Venus Morning Star Missions, wanted to focus on smaller space missions that can build off one another rather than waiting four decades to send a ginormous mission that would be very cumbersome. So this first mission is a small probe, about 40 centimetres wide. It’s cheap and fast, and it doesn’t even have a parachute. It’ll drop into the Venusian atmosphere and slow down naturally from drag.

Inside, there’s one instrument, weighing about a kilogram and sealed inside a pressure vessel. As it rushes through the clouds at 340 kilometres per hour, it’ll shine an ultraviolet laser out a small window, constantly scanning. We’re looking for fluorescence, the same effect that makes your shirt glow under a blacklight. Certain organic molecules fluoresce under UV light, so this is one way to find them.

The other thing we’re measuring is how the cloud particles scatter light, and specifically the polarized light that bounces back. No particle scatters light evenly, so just like how raindrops make rainbows, Venus’s cloud particles can reveal what they’re made of based on how they scatter light. We’ll have only five minutes in the clouds, but it’ll be enough.

And what happens if you find something unusual in those five minutes? The next step will be the Venus Morning Star balloon mission in 2031. We’ll drop a balloon carrying 30 smaller probes into Venus’s atmosphere. That’s where we can spend more time in the clouds, about a full week, running real chemistry experiments to search for complex molecules. We’re using balloon tech from Maxim de Jong at Thin Red Line Aerospace, a Chilliwack, BC–based group whose inflatables have lasted up to 20 years in space. Once the balloon is in place, it will scatter maple seed–shaped probes, which will spin as they fall, helping them to stay airborne longer. The idea is to scatter small sensors; that way, we can measure things like wind speed and detect gases across a broader area.

I’ve heard the balloon is constructed with a top-secret material. Any chance you could share any juicy details about it?
We don’t even know what it’s made of! The former Soviet Union balloons were covered with Teflon, just like in your frying pan, which is resistant to sulphuric acid. But I really can’t say for certain. Whatever it is, it’s good at holding helium.

What are you hoping to find? We’re hoping to be blown away. I want to find a rich diversity of complex molecules in Venus’s clouds, so many that it feels like we’ve hit a gold mine. If you’re panning for gold and just get a speck here and there, it’s hard to know what it means. But if there’s gold everywhere? That’s a sign of life.

Do you and your team want to find a place for humans to live someday? Right now, the goal is only to discover life. We want to know we’re not alone in the universe. There has to be other life out there. If even primitive life exists, then that means there’s probably intelligent life somewhere else. An organism on Venus would have to function so differently than one on Earth that it would have a completely different makeup, right down to its biomolecules. That, in turn, would prove that life had a second genesis—it originated independently in two places. And if it started in two places, it could start in many. That’s really what we’re after.

Do you have any personal, unprofessional stargazing spots in Toronto? It’s hard to see a lot of stars from Toronto, but public parks are good. I used to love taking my dog to High Park at night, and I still spend time gazing north of Toronto one or two times a year. I would encourage everyone to just look up, wherever they are. Each star is a sun. As far as we can tell, most stars have their own planets. So look up at those stars and wonder what kinds of planets could be there. Maybe there’s another Earth. Maybe there’s another Venus. And they’re just waiting. I like to think someone’s out there waiting for us.

This interview has been edited for length and clarity.