A research team has discovered a possible biomarker indicating life in the atmosphere of the exoplanet K2-18b. The research leader wants to collect more data.
Cambridge— A research team has once again found possible evidence of life on an exoplanet—and once again, the focus is on the exoplanet K2-18b, located 124 light-years away. It has been in the scientific spotlight for some time because researchers suspect that life could exist there. Now, a research team has analyzed data from the James Webb Space Telescope (JWST) and made an important discovery: There is a “chemical fingerprint” of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) in the atmosphere.
Both molecules are considered “biosignatures” in astrophysics, evidence of the possible existence of life. On Earth, DMS and DMDS are formed through biological processes, primarily by phytoplankton. This is not the first time that evidence of DMS has been found in the atmosphere of the exoplanet K2-18b. The research team, led by Nikku Madhusudhan (University of Cambridge) had already found initial evidence of this molecule in previous observations of the exoplanet.
Is there life on exoplanet K2-18b? Research team discovers clues
“We didn’t know for sure whether the signal we saw last time was due to DMS, but just the hint of it was exciting enough for us to take another look with JWST and another instrument,” explains lead researcher Madhusudhan. This time, however, a different JWST instrument was used, which is why the researcher emphasizes: “This is an independent detection using a different instrument than before and a different wavelength range of light, with no overlap with previous observations.” The scientist emphasizes: “The signal was strong and clear.”
The concentration of the two molecules in the atmosphere of K2-18b is quite different from that on Earth, according to a press release on the new study . While on Earth it is less than one part per billion, the concentration on the exoplanet is estimated to be a thousand times higher.
Is DMS an indication of life on an alien planet?
“Previous theoretical work had predicted that high concentrations of sulfur-containing gases such as DMS and DMDS are possible on Hycean worlds,” explains Madhusudhan, who is part of a research team that previously identified K2-18b as a Hycean planet. “Now we’ve observed it, consistent with what was predicted. Based on everything we know about this planet, a Hycean world with an ocean teeming with life is the scenario that best fits the data we have,” says Madhusudhan.
But the researcher curbs the euphoria before it can arise: Before one can say that life has been discovered on another world, more data must be collected. After all, previously unknown chemical processes could also be at work, which create the DMS/DMDS molecules. “Our work is the starting point for all the studies now required to confirm and understand the implications of these exciting findings,” says co-author Savvas Constantinou (Cambridge).
The research team is skeptical itself – just like other researchers
Madhusudhan emphasizes, “It’s important that we remain highly skeptical of our results, because only through repeated testing can we reach the point where we can trust them. That’s how science should work.” It’s not just the research team that discovered the exoplanet K2-18b that is skeptical—uninvolved colleagues are also expressing caution. After all, there is now evidence that DMS can arise even without the involvement of life.