You're listening to TED Talks Daily. I'm Elise Hume. Those of you who geek out on science are going to love today's talk. You're about to hear from Clara Susa Silva, who looks for signs of life, beyond Earth. In her talk recorded for Ted Monterey 2021, the quantum astrochemist teaches us what she's learned so far about ecosystems on other planets.

And what that has taught us about how they could support life.

It's my job to find aliens.

So, as you might guess, I spend a lot of time thinking about them, imagining little green women,

meeting up with their friends, commuting to work.

And that gets me thinking about alien astronomers trying to find us and their night sky.

If these alien astronomers had looked in our direction in the last century,

they would have been really excited to detect unequivocal signs of technology.

But what if they looked 10,000 years ago before we showed signs of civilization?

Would they shrug in disappointment and go look elsewhere for life?

No, and neither should we.

Instead, we can look for other signs of life. For example, if those alien

astronomers had looked our way 10,000 years ago, they might notice that even without signs of

civilization, we still looked slightly unusual. For one, we have a thick and temperate atmosphere, but more notably, we have

suspiciously large amounts of oxygen in the atmosphere. This would be a really encouraging

sign of life for my alien colleagues, because the composition of the Earth's atmosphere can

only sustain itself through a biological cycle.

So can we do the same to them?

I'm certainly trying.

I'm a quantum astrochemist, which means I study the quantum interactions between molecules and light in space.

We can't see these molecules, or even the planets there on. But when light from a star

goes through an alien atmosphere, each molecule within it leaves a unique fingerprint in the starlight

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