Lisa Kaltenegger is an expert on the hunt for extraterrestrials – and says the biggest surprise would be if there’s nothing out there
TELEGRAPH
“Generally, when I’m on a plane, if I tell somebody that I search for life on planets around other stars, I don’t get to sleep,” says Lisa Kaltenegger, with a laugh. “It’s always a careful, curated answer depending on if I need to do something next morning when I arrive or not. People are like, ‘Oh, I read about this,’ you know, ‘Have we been visited? Is this true?’”
Outside of her need for sleep, Kaltenegger loves those questions. The 47-year-old professor of astrophysics is a pioneer and world expert on the search for extraterrestrial life. As the author of Alien Earths: Planet Hunting in the Cosmos (Allen Lane), Radio 4’s Book of the Week next week, she is well aware that her chosen field of study taps into a deep and abiding human fascination – are we alone in the universe or is there life elsewhere?
And as the director of the Carl Sagan Institute at Cornell University in Ithaca, New York, which brings together scientists from many separate disciplines to collaborate on the search for life among the stars, she’s better placed right now to answer those questions than almost anyone on Earth.
When I catch up with her over Zoom at her home in Ithaca, she’s just got back from a three-week lecture tour in New Zealand, and a trip up to Burlington, Vermont, “where we had an incredible eclipse. It was beautiful.”
She’s upbeat, passionate, physically expressive. Evidence of alien life, she believes, is tantalisingly close. Kaltenegger is looking for “biosignatures” – telltale signs of life in the atmospheres of distant planets, the sort of gases that organic processes create on Earth, oxygen, methane and others. “We actually have a tool [for finding them],” she says. “And a lot of people don’t realise we do. We have the James Webb Space Telescope, which has been up in space for about a year. We live in this era of golden exploration, with thousands of other worlds on our doorstep, that we now can actually explore.”
Alien Earths is in the best tradition of pop science – bringing water worlds, planets of lava, and the possibility of blue dots like our own before our eyes in a way that is never dry or impenetrable. Kaltenegger is a natural communicator; one of the classes she teaches at Cornell is the introduction to astronomy for non-science majors – “I love being able to change their view of the cosmos,” she says. She took her nine-year-old daughter out of school to go to New Zealand; it was the perfect way to show her the world is a sphere, she says, “to set those physics concepts” on the planet on which we live.
No one should run away with the idea that Kaltenegger is a wide-eyed believer in UFOs, alien visitors, abductions and the rest. In fact, she begins her book by sweeping from the table all the “evidence” put forward so far. She recognises that UFO hunters are responding to “the excitement of trying to find life in the universe”, but “a lot of times with UFO sightings, the data is just not good enough”, she says. “If you have a smudge on a photo, it is interesting, but…”
This turns out to be a big “but”. One has to understand all the variable factors of a sighting, Kaltenegger explains, light reflection, weather patterns, how far away something is if it appears to be moving really fast. In her book, she notes, “I’ve basically said, this data is not good enough for us to make any conclusions.”
What then, of the former US Air Force officer David Grusch, who testified at an American House of Representatives sub-committee last year that, in his time on the Unidentified Aerial Phenomena Task Force, he had seen documents that showed the existence of a secretive UFO-retrieval programme; that America possesses multiple spacecraft of alien origin and that “non-human biologics” were found at an alien crash site?
Kaltenegger wrote her book “a little bit with that in mind”, she says. “Because I think people are very, very smart, and actually do start to doubt these things when it’s just a little too convenient. But there’s not much out there that’s easily accessible that tells you, be careful if somebody wants to sell you this and what are the questions you should ask.
“When I see that [testimony], honestly what I think is, ‘Oh God, I wish this were true.’ That would be so much easier if we had aliens coming here. Because the search for chemical make-up, and gas as a biosignature, it’s hard, even with the biggest telescopes we have.”
The idea that we are constantly being visited by interstellar entities, she suggests, begs the question, why? – given the technological gulf between us and any intelligent life-form capable of interstellar travel. “We are in the infancy of space exploration. We have boots on the moon, but we don’t even have boots on Mars,” she says. “We are not the place that you would go to.”
All this plays in her head when she sees pronouncements like Grusch’s, she says. “This is where the scientific method is so important. This snake oil is probably not going to help you.” If it was their health, people would ask for a second opinion, she stresses. “It’s funny that some people suspend that thinking when it comes to somebody trying to sell them evidence of alien life.” At the very least, she says, people should not give it credence without a “second independent team for us to confirm it. That’s the least thing.” Her own methodology, she says, “is a much stronger evidence-based search tool”.
Even for scientists prepared to put their evidence for extra-terrestrial life into the public domain, she suggests, the bar remains high. Harvard science professor Avi Loeb caused a stir with his 2021 bestseller, Extraterrestrial, which suggested that an unusually thin stellar object spotted moving away from the sun millions of miles from Earth in 2017 was an alien light sail, propelled by solar radiation instead of wind.
“I think Avi really wants to be the person who finds life in the universe,” Kaltenegger says, with an expression that could perhaps be interpreted as a groan, “[when] people looked at it and said, it couldn’t be [what Loeb claimed] because of the way it moves, at that point, I think as a scientist, you are trained to accept the death of a beautiful hypothesis by an ugly fact, and you move on to the next thing… I think at some point, as scientists, we know better. Chances are, it’s not a light sail.”
In Kaltenegger’s world, though, there is excitement about four potentially life-supporting planets found orbiting the red dwarf star Trappist-1, a mere 40 light years from Earth, in 2017. “The James Webb Space Telescope is observing these planets right now,” she says. “We have a chance to find the gases on these worlds. And to figure out if there’s biosignatures on them within the next, let’s say, five to 10 years.” The time frame, even with the wonders of a space telescope, is necessary because of the difficulties of building a clear picture of an exoplanet with so much light interference from the star itself. It takes time.
But, Kaltenegger says: “If life is everywhere, it can be in that system. It may be that we need to observe 100 systems before we find life, or 1,000. But it could also be that we just need to observe one system.” If that’s the case, she says, then the announcement that we’re not alone, “could be just a couple of years from now”.
When Kaltenegger was a girl growing up in the small Austrian town of Kuchl, in a quiet river valley beneath the Berchtesgaden Alps, the idea that her horizons would one day expand to the furthest visible planets beyond our own solar system was unimaginable.
Her father was a civil engineer and her mother a secretary; her elder sister is an architect. Kaltenegger was “always really curious” about the world around her, she tells me. “I was one of these kids with all the questions.” By the age of 10, the local library had given up trying to put limits on the number of books she could borrow. Yet it would be another five years before the first exoplanet – a planet outside our own solar system – was even found. And it wasn’t until her first year at university in Graz, where she studied astrophysics, that the first exoplanet orbiting a sun-like star was discovered, in 1995, in the constellation of Pegasus.
The Alexandrian astronomer Ptolemy had identified the constellation as far back as the second century, yet the discovery of this planet, 51 Pegasi b, was a game-changing revelation. Still, Kaltenegger felt, “this was something that Nasa did, that the big countries did, I was studying in Graz, which is a pretty tiny town”.
A year later, she travelled to a conference on “Planets Outside the Solar System” in Corsica, by package flight and bus, and met “this really small community of people who were asking all these questions for the first time, you know, what does it mean? Could there be more planets out there? What are the things we should do? It was a very flat hierarchy – the professors would ask the students what they thought, what I thought. I was an undergrad in my second year… The discussion was so fascinating.”
She soon realised, “to understand a planet, you have to understand the star, you have to understand the geology, you have to understand the biology that’s going on… I was basically thinking, this will never get boring.”
Within a few years, she had gained a doctorate in astrophysics, and at 27, moved to Harvard University; in 2010, she took over the leadership of a research group at the Max Planck Institute for Astronomy in Heidelberg, in Germany, before taking up the post of associate professor of astronomy at Cornell.
Along the way, Kaltenegger has encountered sexism many times. “It got a lot better. It’s still not that great sometimes.” She describes how in her first week working for the European Space Agency, her boss had forgotten to copy slides for a meeting with aerospace engineers, but insisted that she not go off to copy them for him, telling her that if she was seen to be doing the copying, whatever she did subsequently, they would always see her as the secretary. It’s essential to challenge sexist attitudes whenever they are expressed, she says, because “if nobody speaks up, they interpret it as everybody agrees with them and that’s not the case”.
“I would say that 80 or maybe even 90 per cent of people think that women in science are capable. And they do understand that it’s historically coloured, that you don’t have as many women with big breakthroughs, because they had such a hard time getting into the field. And if they were in that field, most of the time, they didn’t get the acclaim for whatever they did discover, somebody else did.”
It was her sense of a need for an interdisciplinary approach that became the seed for the Carl Sagan Institute, which she set up in 2015, becoming its founding director: “No one person can know all of science any more,” she says, “so I built this institute with about 15 different departments ranging from astronomy, geology and biology to music and performing arts to interlink that information.”
There are now more than 5,000 confirmed exoplanets, which can be studied in ever greater detail, as more powerful telescopes become available. And the search for evidence of life on these planets has narrowed to ones in the “habitable zone” of a star system – often referred to as the “Goldilocks” zone, because it’s “not too hot, not too close to the star; not too cold, not too far away”, Kaltenegger explains. In fact, the conditions are just right.
“What we know is that around every fifth star, there’s a planet that’s in the habitable zone and small enough to be a rock,” she says. “And our galaxy alone has 200 billion stars. So one out of five gives you billions and billions of opportunities.” She’s clear about what that means about the search for alien life. “I think the biggest surprise would be if we found nothing.”
She knows, though, that there are scientists who have cast doubt on the validity of “biosignatures” as definitive proof of life, who suggest that the possibility of chemical processes that produce the same composition of gases cannot be ruled out. Kaltenegger embraces scientific scepticism: “I think the brutality of the scientific method is really important, especially if you wish to find something. Scrutiny is science’s biggest strength, because it cuts off the wrong answers. However, I think we do, currently, have some combination of biosignatures, the combination of oxygen and methane, that under specific circumstances, if the planet is within this habitable zone, we have no other explanation than there being life.”
The certainty may not be 100 per cent, she says, but if the likelihood reaches 95-99 per cent, then it will cross the threshold for scientific confidence, because any other explanation would rely on “a really exotic geochemistry that we don’t understand and have never encountered… It will depend very much how many of these planets we find. If we find lots of planets with signs of life, to have an exotic geochemistry that works just so for each of those is going to be super unlikely.”
I want to ask Kaltenegger about the scenario in the 1996 film Independence Day and so many others: are we making a mistake searching for alien life, given our own violent, rapacious qualities as a species – is there any reason to think intelligent alien life would be benign? In 2011, the physicist Stephen Hawking said that “the numbers alone make thinking about aliens perfectly rational” but suggested, “If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.”
Kaltenegger enjoys science fiction and says that if aliens do visit earth, the military helicopters and quarantine zones of Contact (1997) and Arrival (2016) are “definitely something that I think would happen”, but she’s not buying the Independence Day scenario.
As for trepidation about making contact, she notes, “the cat’s already out the bag”. She explains that a technological civilisation could easily have used “biosignature” techniques to observe Earth and see that it supported life a very long time ago.
“In my first real scientific paper from 2007,” she says, “we figured out that for about two billion years in Earth’s history you could find the combination of oxygen and gases that are the golden fingerprint of life. If there’s somebody out there, I don’t think announcing our presence would make any big difference. Because if they just had our level of technology, they’d know we’re here. It’s been two billion years, and nobody has come to eat us yet.”
I wonder what she makes of Elon Musk’s Space X project and his plan to build a sustainable colony on Mars. “I don’t want to live on Mars,” Kaltenegger says. “I think it will be incredibly hard because you can’t breathe, so that’s a completely different step in exploration than we’ve ever had before – even at the North Pole, you can breathe. But I think if somebody wants to do it, it’d be quite interesting. I think space exploration actually has great benefits.”
