Will we find alien life in the next 25 years?

With all the talk of distant star systems and galaxies, the subject of habitable exoplanets and extraterrestrial life inevitably rears its head. And the JWST has been a huge contributor to this wave of planetary discoveries. To talk through just how the James Webb is helping us look for signs of life, and some of the most promising findings, is space scientist and author, Dr David Whitehouse.

David - I think the most outrageous way is if it saw something strange in one of its images, what's called a techno signature. Because there are ideas in science fiction that when civilizations get very old, very accomplished and they can do great things, they might start to rearrange a solar system. It has happened a few times in the past with other telescopes seeing strange things in the sky, but they've always been explained as natural phenomena. But it's not breaking any rules of science or physics to suggest that someday some astronomer might look at some object, look at the data from some object and say, 'that looks pretty strange. Does that show any sign of intelligent interference?' But that is the science fiction end of it, and no telescope is designed to do that. What the James Webb telescope is designed to do exceptionally exquisitely brilliantly, is to analyse light. It's got two spectrographs, which takes the light in various parts of the infrared spectrum and splits them into the component wavelengths. And every molecule has a spectral signature. Methane, carbon dioxide, they're all identifiable in a spectra. So if you want to either look at a planet on its own, if it's sufficiently far away from its host star and you can look at the light from it directly, you can then analyse that light. Or sometimes, as is often the case these days, you see a planet that moves in front of its star and causes the star to dip in brightness. because it's obscuring some of the star's brightness. And by a fancy bit of footwork of analysing the light when the planet is in front of the star to the side of the star and perhaps behind the star, you can actually pull out the light from the star that's travelling through the planet's atmosphere. And then you can look for these absorption lines, these spectral signatures. And that's been done a couple of times with James Webb with very interesting results.

Will - When we single out all these molecules that we think might be the giveaway as to signs of life, which molecules exactly are we looking for?

David - Well, we're looking for carbon dioxide, we're looking for methane, we're looking for oxygen. We're looking for ozone, we're looking for nitrogen dioxide. They're fairly common molecules, but they are very good indicators of surface environments. And you can work out the physical characteristics of the surface of the planet. If you have other indications for instance, there was a planet called A218B, which was recently very much in the news because they found evidence of methane water vapour. And some people suggested hints of a molecule called dimethyl sulphide, which is only produced by life on planet Earth. So that obviously caused a great deal of discussion because here you have a planet which has a molecule, which on Earth is associated with life. But there had to be caveats with that because when you look at the analysis, the dimethyl sulphide's spectral signature, its barcode if you like, straddles several detectors. And if you don't individually calibrate those sensors, you might get the wrong impression. You might not get a good signal if you don't calibrate them. You see the signal of dimethyl sulphide, when you calibrated them properly, the signal was much, much less impressive. So although it's not been ruled out, it's certainly not been discovered, but it does indicate the power of James Webb.

Will - One of the most striking things about the planet you mentioned, whose name escapes me briefly, is that it was, universally speaking of course, fairly close to us and it kind of implies that there's a lot out there that may even be able to harbour life. That could be within travelling distance.

David - Yes. I mean, K218B was I think a hundred and twenty, a hundred twenty four light years away, fairly close. But there's an even better one called VHS1256B, which is a Jupiter sized object, but it's only 40 light years away. And we've got some fascinating observations of the atmosphere of this world. But the interesting thing is that it's thought that within about 50 light years of the earth, there are 40, 45 exoplanets that we know of, and there are bound to be more yet to be discovered. But given the capabilities of the James Webb Space Telescope, the fineness it can read the barcode spectra from atmospheres of exoplanets, you're probably talking 50 light years away as being the farthest you could do this. So that shows that our candidate stars with planets and interesting planets with interesting environments within reach.

Will - And as a final bit of complete speculation, there have been some fairly outrageous claims recently that because of James Webb and all the capabilities we now have, we may well be less than 25 years away from finding life on another planet. What is your take on that?

David - Well, who knows is the answer to that. And it's nothing you can put your finger on. We may discover life tomorrow. We may not discover life for decades, and that would tell us something very important about our universe. But I think every astronomer wants to make an observation to look at some data and have that little sort of question mark in the head which says, that's interesting. I wonder what that was. And when I was a professional, full-time astronomer, we all had in the back of our minds, is this the observation? Are we going to be famous astronomers to find life? Of course, nobody has been, but I think most astronomers have got that sort of excitement whenever they look at a new bit of data.