Scientists questioned the discovery, which became sensational in April. The signals obtained by spectroscopy of planet K2-18b may belong not only to two substances that are formed due to the activity of living organisms, but also to many others.
Life signs on K2-18b
In April 2025, news from a research team led by Prof. Nikku Madhusudhan of the University of Cambridge became a sensation. After all, it showed that there were signs of life on the planet K2-18b, which is 124 light-years away in the constellation Leo. However, this conclusion has now been called into question.
Scientists then used the James Webb Space Telescope to investigate the chemical composition of the atmosphere of this world discovered years ago. The most important result was the peaks in the spectrogram, which were identified with extremely high confidence, at the 3 sigma level, as dimethyl sulfide (DMS) and dimethyl disulfide (DMDS).
At the same time, scientists have not claimed to have discovered alien life, as many questions remain about the planet itself. However, if their data is confirmed, this could be a really strong indication of its presence — after all, on Earth, both of these substances are formed solely by biological processes.
It’s not that easy
And now two former students of Madhusudhan have conducted a new study and questioned the very interpretation of the findings as the presence of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS). The fact is that the conclusions from the original study are actually statistical in nature. Then scientists checked about 20 substances that can give such a picture obtained by the James Webb Telescope, and the two that became a sensation turned out to be the most likely explanation, and by a wide margin.
However, in the new study, the scientists took the same data set from the space telescope and tested a much larger number of connections, and used a slightly different data processing mechanism. First it turned out that there were about 90 substances that could theoretically explain the observations, then about 360. And that in itself has already dealt a blow to the validity of previous results.
The results of the analysis showed that dimethyl sulfide was present among the three most probable substances that could explain the obtained spectral pattern, but dimethyldisulfide was absent. It is dimethyldisulfide that provides the strongest evidence for the possible presence of life. But two other potential compounds are diethyl sulfide and methyl acrylonitrile.
The latter is toxic in general, and although it looks too exotic to be present in the atmosphere of K2-18b, the prospects for life on it, already uncertain, become even more unlikely.
In fact, this is not the first article questioning the findings that caused so much buzz in April. However, the authors of the original study so far either reject all objections or choose not to comment at all.
According to phys.org
