The search for life beyond our own planet is something that astronomers have been doing for decades now, with no results.
But on April 17, a study was published revealing that a team of astronomers using the James Webb Space Telescope (JWST), led by Nikku Madhusudhan, had discovered gases on an exoplanet called K2-18b that could only be produced by life.
Right off the bat, many astronomers were a little skeptical about the claim, saying there wasn’t robust evidence to support the findings.
“Discoveries like this … usually takes a long time to confirm, and many times it turned out not true,” Yanqin Wu told CBC News on the day it was announced. “That’s just the disappointment in real scientific endeavour. Extraordinary claims usually takes a lot of proof and usually are wrong.”
Now, a new independent analysis of the JWST data has found no evidence of biosignatures, signs that the planet’s gases may have a biological origin.
Madhusudhan and his colleagues used data collected from JWST of the planet passing in front of its host star, K2-18, and the different molecules that were observed in the spectra. This method is useful for determining which chemicals are in the air of a planet.
The study found the presence of two gases — dimethyl sulfide, or DMS, and dimethyl disulfide, or DMDS — which are typically produced on Earth by algae.
But Jake Taylor, a planetary scientist who also studies exoplanets using JWST data, used that data and examined it using a different method than the Madhusudhan-led study and was unable to replicate the findings. He published his results on the pre-print site ArXiv.
Prof. Nikku Madhusudhan, a Cambridge University astrophysicist, says the discovery of two gases — dimethyl sulfide, or DMS, and dimethyl disulfide, or DMDS — in the atmosphere of a planet will be seen as a ‘paradigm shift in our search for life.’ Scientists used NASA’s James Webb Space Telescope to make the discovery about K2-18 b, a planet found about 124 light-years from Earth.
In his method, he used an “agnostic” approach, meaning he didn’t look for any sulfur gases that could be signs of life like there are here on Earth. The result was a “flat line” rather than any wiggles in the data, meaning that the dips found in the initial study were statistical noise — random information that can effect study results.
Taylor said he was excited about the study and thought it was good in some ways, but “when it came to the atmospheric physics side, I noticed that they didn’t give too much detail about their flat-line rejection tests.”
He explained these tests are “kind of a standard within the field” to do first in order to ensure there isn’t noise in the data.
He said he did speak with Madhusudhan personally about this last week, who reassured him that the rejection tests had been conducted, though they weren’t contained in the study itself.
Though he said the current data from JWST didn’t provide enough confidence in a biosignature detection, it doesn’t mean it couldn’t happen with additional data.
“It’s a good first step in in this sort of endeavour, because this is a spectral range we’ve never seen before. So just that in itself is pretty cool,” Taylor said. “We definitely would need more observations to get a better signal. And who knows, it might pop out, it might be there. It’s just right now, the signal-to-noise ratio is not definitive.”
Asked if there needs to be more rigorous examinations of such claims, Taylor said, “I think there needs to be more discussions about this. I do personally think that there needs to be multiple lines of evidence, and also there needs to be like a model independent confirmation that we see something.”
Taylor admitted he was a big fan of The X-Files, a sci-fi show that largely focused on finding proof of alien life on Earth. Its most touted catchphrase was “I want to believe.”
He also noted that planetary scientists looking for signs of life on exoplanets do really want to one day find that robust sign of life, though it’s not like we could ever visit the exoplanet to confirm with certainty.
“We want to believe,” he said. “But we want to do it correctly.”
