ALONE IN THE DARK?

Lisa Kaltenegger, an astrobiologist who spends her days looking through powerful telescopes, says signs of alien life at the edge of the universe are becoming clearer every day

- Lisa Kaltenegger

We know that one out of five stars has a planet that could be like the Earth’s. It’s incredible. One in five – and we have 200 billion stars in the Milky Way, alone. So there are 40 billion possibilities for worlds like ours just in our galaxy.

I’m part of the Near Infrared Imager and Slitless Spectrograph (NIRISS) team, which is one of the instruments on the James Webb Space Telescope. We are looking at the Trappist-1 system right now – the first rocky worlds that are within this habitable zone. So, we’re already looking at some worlds that could harbour life.

Right now we are concentrating on gases – what’s breathing in and out. It’s like when you go into the forest and see footprints. You can say, ‘Oh, this is definitely a deer.’ But if you see something else – smudges in the dirt, for example – it could be life, but it could be something else.

So we make our telescopes look for life as we know it – while keeping our eyes open for anything weird or unexplained. You have to be very careful about interpreting signs of life that you don’t understand because there are other explanations like a kind of geology that’s not part of our planet and that you just haven’t thought about.

Life on Earth needs water, but water alone isn’t enough... Hopefully, we will find oxygen, but oxygen alone is not enough either. We’d also expect to find methane.

This is why early on I started to make these models of Earth through its geological time to figure out how long you could have spotted this life fingerprint here. Nobody had done this before. How long could you have seen that Earth was a habitable world? We came up with 2 billion years, because that’s how long the combination of oxygen and methane left an imprint in our air of life on this planet.