Possible 'Hints' Of Life Found On Planet 124 Light-Years Away In James Webb Space Telescope Data

Space.com

Data from the James Webb Space Telescope on exoplanet K2-18b has revealed the "strongest hints yet of biological activity outside the solar system," according to a University of Cambridge study.   Credit: University of Cambridge

Transcript

00:00We found the strongest evidence to date of possible biological activity on an exoplanet.

00:13DMS stands for dimethyl sulfide. This is a very important molecule because here on Earth,

00:26DMS is produced uniquely by life, microorganisms in the ocean like algae, phytoplankton,

00:33and theoretical studies have predicted for the last two decades that molecules like DMS would be

00:39very robust biomarkers on exoplanetary systems, including planets with hydrogen-rich atmospheres

00:46like Haitian worlds.

00:54K-218b is an exoplanet orbiting a red dwarf star about 124 light years away. It has a mass of about

01:028.6 Earth masses and a radius of about 2.6 Earth radii, and it orbits in the habitable zone of its

01:10host star, which means if you put an Earth-like planet at its location, we would think of it as habitable.

01:16So the technique we used to determine the atmospheric composition of the planet is

01:26known as transit spectroscopy. What is happening is that you look at the planet as it transits in

01:31front of the host star. So the atmosphere of the planet, some of the star light goes through the

01:38atmosphere of the planet before reaching the telescope, and the atmosphere, the molecules in

01:43the atmosphere absorb some of that star light. So by looking at a differential measurement when the

01:48planet is in front of the star or when it isn't, you can extract how much absorption is happening in

01:54the planet's atmosphere.

02:01So two years ago in 2023, we reported a very tentative inference of DMS on this planet with a different

02:09set of observations with a different instrument in the 1 to 5 micron range. But the evidence was very

02:14tentative, so we looked this time at the planet again in a different wavelength range. And what we are finding

02:22is significantly stronger evidence at a three sigma level for the presence of either DMS or DMDS or both.

02:30Now DMDS, like DMS, is also a strong and unique biomarker here on Earth and had also been predicted

02:37to be a biomarker on planets with hydrogen-rich atmospheres. And that is what is new, is that there's a

02:42possibility of one or both of these molecules to be present in the atmosphere at a credible

02:50level of significance. So while this is great and evidence to keep looking, this is not enough to

02:58qualify it as a robust scientific discovery. For that we need to reach the level of five sigma. What does

03:03that mean? At five sigma you're talking about the chance of a fluke being about a part in a million.

03:16So we are pretty confident about our results at the significance that we are finding at this three

03:21sigma significance and that's partly because we have done enormous number of robustness checks. We

03:27have done it with multiple pipelines and within the same data reduction pipeline we have tried various

03:33assumptions on how we can reduce the data and no matter how we did it the signal always persisted.

03:40And to us that's a great measure of our confidence in in the detection at this level. But we should

03:46remain open-minded and get more observations so we can repeat the signal. That's the hallmark of science,

03:51the repeatability and increase in robustness till we get till we are really really satisfied. We are not there yet.

04:03So the question you may have is, have we found life on another planet? And this answer is simply no, not yet.

04:09Right? So we have to, as I always say, we have to be very careful in two directions. The

04:16detection we have made is at a level where it is very interesting. It's a landmark result, but it is not

04:24good enough to call it robust just yet. This is a big signal we are looking at. This is of very high

04:31importance. We need more observations to get it to that five sigma level where we would be much more

04:36confident, number one. And the second aspect of that is that when we do detect and while we are making

04:42these observations, we also have to remind ourselves that while DMS has been predicted to be a robust biomarker,

04:48there is always a possibility that we may not have accounted for some physics that we don't know

04:54so far or some chemical process that we don't know of. So we want to remain open and do as much

05:00theoretical, as many theoretical calculations and lab based studies to say if there is any process

05:07which can get DMS in such an atmosphere at the levels that we are seeing.

05:10This is one of the most profound moments for me personally, as well as an astronomer,

05:25because for the first time in the history of our species, we may actually be seeing signs of life

05:32elsewhere. On the other hand, this could also be a signal of a new chemical process

05:40that is not produced by life. And even that is a monumental breakthrough because however

05:45you put it, we are seeing new chemical processes on a planet that could be habitable. And we have

05:51shown this in theoretical studies that that was possible. So this is, in my view, a transformational

05:58moment, not just for planetary science, not just for astronomy, but for finding our place in the universe

06:05as a species.

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