Science & Nature
Cambridge Astronomers Detect Tentative Signs of Life on Distant World
Scientists at the University of Cambridge in England said they have detected possible signs of life in the atmosphere of a distant exoplanet called K2-18B.
Using the James Webb Space Telescope, researchers said they were able to detect signs of sulfur-based molecules called dimethyl sulfide or DMS, which on Earth are only produced by life, primarily marine phytoplankton.
The Cambridge team said it reached a “three-sigma” level of confidence in the findings — meaning there is a 0.3% chance the findings are a fluke.
In the interview below, Michelle Nichols, director of public observing at the Adler Planetarium, talks to WTTW News about her take on the Cambridge team’s findings.
WTTW News: Scientists at the University of Cambridge have used the James Webb Space Telescope to detect what they say are possible biomarkers on a planet called K2-18B. What is known about this planet?
Michelle Nichols: So that particular planet is bigger than Earth and smaller than Neptune. The star that that planet orbits is 124 light years away, and the type of star is called a red dwarf, and so that means it is a cooler, smaller star as compared to our own sun.
K2-18B orbits the star at a distance where the planet’s surface temperature could support liquid water. It doesn’t necessarily mean that liquid water is there, but the surface temperature, it’s at the right distance away. It’s not too close to where it would be too hot and anything would boil away. It’s not too far away where it would be frozen. But the planet itself is somewhere around 8 or 9 times as massive as Earth.
There’s some estimations that based on some of the signatures that we’ve seen from observations of that planet, that they have detected methane and carbon dioxide. So one of the ideas of this world is it could be that it has an atmosphere that is rich in hydrogen with a global ocean below that atmosphere. That’s one way of interpreting the data. Another possibility could just be the surface is a global magma ocean. So liquid rock covering the entire planet.
Less hospitable to life, presumably.
Nichols: Oh yeah, that would be really tough.
How can we detect what’s in the atmosphere of a planet that is so far away?
Nichols: So we don’t see most of these planets directly. Most planets around other stars have to be detected indirectly and the type of method that’s used most often is called a transit, and you can think of a transit like a little tiny eclipse. If we detect a planet, that transit method means that we see the light from the star drop a little bit as the planet blocks a little bit of the light. And if we see that happen periodically, we know there’s a planet there. Then, in order to figure out if the planet has an atmosphere, you can detect the light from the star separately. Then you can wait for the planet to pass in between Earth and the star, and we can see then if there is an imprint of the light that happens to pass from the star and through the planet’s atmosphere, and that light comes to us as well. So that means the light that we get in total will be just a little bit different because it has imprinted that information about what’s in that atmosphere. We compare those pieces of information, and we can see if some of these planets, if they’re close enough to us, we can see if they have an atmosphere, and in some cases, we can start to tell what that atmosphere is made of.
Obviously the reason this has made headlines around the world is because of the idea that it could possibly be signs of life. As a professional astronomer, how confident do you think we can be in these findings? And if they are confirmed, how significant do you think they are?
Nichols: So they haven’t yet gotten to the point where they can say for sure that DMS and DMDS (dimethyl disulfide) are even there in the first place. They’ve gotten closer to being able to say that, but it’s still very weak hints that that stuff is even there. So they still need to get to the point where they consider it to be scientifically significant. So 99.99999% sure. Right now they’re at 99.7% sure — and that’s not good enough for convincing scientists that this stuff is even there to begin with.
So then let’s say they get to that 99.99999% sure that it’s there, that doesn’t tell you what’s making those materials. And yes, on Earth, those two materials are produced by a certain kind of life, (but) that does not preclude that there are other processes that exist on these other planets that are quite a bit different than our own planet. We can’t just assume that, oh, if we just see this then life is the only way of making those materials. It’s not. And then let’s say they do get there (in terms of being 99.99999% certain), what this really is saying is not that life is out there. It’s detecting molecules that could be signs of life elsewhere. … We then have to cross the really big step of (analyzing) all the possibilities of how you make that stuff without life or with life, and then you need to start picking all that apart.
The way I put it is we’re casino sure. Like if you had a 99.7% chance of winning at the casino you would take that. … But scientists have got to be even more sure that what you’re finding is there. Otherwise, all you’ll say is it might be there.
The scientists at the University of Cambridge, they’re not claiming to have discovered life, but at the same time, when you put out a press release saying we may have found tentative signs of life, clearly the media has gotten very excited. But do you think the scientists themselves may have got out ahead of their skis a little bit on this?
Nichols: I think their enthusiasm outweighed their results, but it just shows you that they’re just really excited about this whole process, and I think they want everyone else to be as excited… and so they’re so excited, you can tell, but they’re just not there yet in terms of the data holding up.
Obviously people are incredibly excited about the possibility of detecting life. And there’s detecting signs of life that might be, say, microbial and then obviously the holy grail of detecting intelligent life. How do you think we’re most likely to reach a point where we’re confident that we’re not alone in the universe?
Nichols: I think it would have to be something more along the lines of being detected in our own solar system, but it doesn’t have to be technological or anything like that. It could be something detected in a rock sample that gets brought back from Mars that showed that life existed on Mars in the far distant past 2 billion-plus years ago. Or something as we study Europa (Jupiter’s fourth largest moon that is believed to have a water ocean beneath a surface of ice). We just need to find life in one other spot. It does not need to be technological. It doesn’t need to be signs of advanced life or even anything like us. It just needs to be life somewhere. And if you find it in one other spot, it means that we very likely are not alone in the universe.
