The astrobiologist Nathalie Cabrol was born in 1963 and raised near Paris. She completed a PhD at the Sorbonne on the evolution of water on Mars and moved to the US in 1994 as a researcher at Nasa Ames. She has worked extensively in the Atacama desert and the Chilean Andes, exploring how life adapts to extreme environments analogous to those on other planets. Cabrol, who lives in Northern California, is now the director of the Carl Sagan Center at the Seti [Search for Extraterrestrial Intelligence] Institute. Her latest book, The Secret Life of the Universe: An Astrobiologist’s Search for the Origins and Frontiers of Life, is published on 15 August.
How did you get interested in the heavens?
It’s not difficult to be interested in the heavens, we are in the heavens! I have a recollection of watching the sky, aged five or six, and starting to ask myself: “What is this all about? Why does this exist?”
When searching for extraterrestrial life, is it a mistake to look only for Earth-like planets and life as we understand it?
It’s not necessarily bad to look at our biochemistry and the kind of environment that brought us here. Astronomy is telling us that the stuff we’re made of is so common, and we’re learning that carbon was created so much earlier than we thought. And with the discovery of exoplanets [planets outside our solar system], we’re also realising that, although there is probably no exact replica of the Earth anywhere in the universe, there are environments that are probably as suitable for life, or more so. But from that standpoint we are bottlenecking ourselves into looking for another version of ourselves. I’m looking more at the universal markers of life – markers that would be true anywhere in the universe, regardless of biochemistry.
What makes you so sure there’s something out there, rather than nothing?
The easy answer is Carl Sagan’s response: “That would be an awful waste of space.” We have been searching intellectually for life for thousands of years, but searching in a meaningful way with technology for only 60 years, so this is a very young search. Also, you have to look at the distances. Even if by some miracle [alien life forms] are thinking and communicating in similar ways to us and are interested in what’s happening around them, our radio bubble is barely 200 light years in diameter. That’s small. Then there’s the fact that we are searching for life but we don’t really know what life is, or intelligence, or even less consciousness. We have no clue what those three things are. We’re still looking for them, which is fine, because otherwise you go nowhere.
Where in our solar system would you most expect to find life bubbling up?
I believe that Mars still has some big surprises for us. They won’t be at the surface, but unlike many people I don’t think it’s going to be that far below. There is still volcanism on Mars and we know that there is water and plenty of nutrients – magnesium, potassium and so on. Elsewhere in the solar system, Europa [a moon of Jupiter] might have an oxygenated ocean that may provide a chance for more complex life evolving. It also has sources of carbon.
We’re talking about oceans under miles of surface ice.
Yes. And the thing is, you don’t have to invest in submarines to explore it; you can let mother nature bring the stuff to you. Because of the gravitational tides on Europa, you have these convective movements and a sort of slush coming regularly to the surface. You land next to it, grab that stuff and look at what’s in there. You let the ocean come to you.
But Enceladus [a moon of Saturn] is definitely my favourite. I love it because it’s just throwing stuff at you in geysers or plumes [shooting up from the surface]. Obviously it’s quite complicated to slow down a spacecraft to grab samples, but we could do incredible things on Enceladus.
Do other planets give us lessons about what to expect from global heating on Earth?
When you look at what happens to a planet when you have a runaway greenhouse effect taking place, then this is Venus. And the planet that’s too hot that’s losing its water, that’s Mars. We have that right in front of our eyes.
What’s your view on people such as Elon Musk who speak of colonising other planets?
Well, first, I hate the word colonising. And the idea of putting outposts on another planet because we are escaping our own is an insult to the spirit of exploration. Migrants usually move because they’re desperate for better conditions. That’s not the case on Mars. It’s much worse. I think that we should go to Mars not because it’s an easy escape, but because we have grown up and we’re using it as a training ground for a much more adult civilisation to take its first steps towards becoming interplanetary, and later on, interstellar. But we should also use all that technology to look back at the Earth.
Projecting ourselves into space is challenging our brains to find solutions that we would not otherwise be seeking on our planet. Certainly, sending a Tesla into space [as Musk did in 2018] was not the right message when you are trying to create space policy and prevent planetary contamination.
There’s been a lot of excitement about UAPs [unidentified anomalous phenomena] recently. Do you give it much attention?
As a scientist, UAPs are interesting to me, because first we have to take them for what they are: unidentified phenomena. The jump I’m not making is saying that they are necessarily extraterrestrial phenomena, as in flying saucers and so on. We know that 96% of them are going to find a natural explanation. One thing to consider is that we are seeing a lot more unusual atmospheric phenomena, because our planet is changing. And then there are undisclosed government activities that you weren’t supposed to see. Finally, there is the half percent or so that is unexplained. Of course I’m interested.
But Seti is not into aerial phenomena – our instruments are pointed much farther away. I always say, joking, that we are looking for ET in its own habitat, whereas people looking for UAPs are trying to see ET in ours. But if you tell me tomorrow that you have irrefutable evidence of an alien spacecraft that’s been captured in a video somewhere, I’ll be the happiest person in the world.