Signs of alien life on exoplanet K2-18b have all but vanished

The hopes of finding extraterrestrial life on the planet K2-18B are quickly struggling, because new observations seem to show any detectable evidence of the previous biomolecule of studies have seen clues. Most scientists agree that this shows that previous affirmations were premature, but one of the researchers behind the previous results maintains that the new data actually show stronger proofs than previous observations.

In April, Nikku Madhusudhan at the University of Cambridge and his colleagues said that the planet K2-18B, AA Rocky Planet larger than the land which is around 124 light years, contained indices of dimethyle of dimethyle (DMS) and DMS) in its atmosphere. On earth, these molecules are only produced by life. At the time, Madhusudhan said it was the “first clues that we see from an extraterrestrial world that may be inhabited”.

However, when other researchers later analyzed these same data from the James Webb space telescope (JWST) using different statistical models, they found no solid evidence of the presence of these molecules. But Madhusudhan and his colleagues also reanalyzed their data in a more global way, which he said New scientist The “more confident” rendering that the DMS was the best explanation of the data. Without new observations from the planet, astronomers could not agree if there were proofs of life on K2-18B.

Now, Renyu Hu at the California Institute of Technology and her colleagues have teamed up with Madhusudhan and his group to analyze the new JWST observations of K2-18B. They found no statistical evidence of detection. “The document does not provide conclusive evidence of the existence of this molecule in the atmosphere,” explains Hu.

Madhusadhan, Hu and their colleagues used the nearly infrared camera of JWST to look at the light of the K2-18B star, which, after having crossed the atmosphere of the planet, can tell us what molecules exist in the atmosphere. This camera examined a light wavelength different from that of the average infrared measures that were used for previous analysis in April. They then tried to explain the data using several different models from the atmosphere of K2-18B, each with different hypotheses, such as those which included different molecules or where the atmosphere of K2-18B was filled with water vapor.

Some of the models that included the DMS could explain the data a little better than the models without it, but it was not always true, and in no case did the statistical evidence succeeded in the threshold of what scientists can call detection with confidence. “This dependence on the model simply talks about the fact that it is a very low signal, if there is a signal,” explains Hu. “I would be cautious.”

Madhusudhan agrees that we do not have enough evidence for detection, but it also maintains that it is more fair to compare this data with the previous observations of the nearly infrared camera of JWST taken in 2023, rather than the data with the average-infrared instrument taken in April, in which case DMS proofs seem stronger. “Purely statistically speaking, based on what we report in the document, the data objectively shows slightly higher evidence for the DMS,” explains Madhusudhan.

“There could still be other molecules that emerge like DMS,” he says, but there is a characteristic of the signal caused by an unexplained molecule, which, according to him, is better explained by the DMS. “But we can obviously obviously not make a robust complaint.”

“This document is very clear by saying that there is no proof of dimethyle sulfide. There is no statistical evidence for any of these gases, ”explains Luis Welbanks on Arizona State University. Sara Seager at the Massachusetts Institute of Technology considers in the same way, saying that the level of statistical meaning that the team has declared “is not considered a detection”.

“We seem to arrive at the end of the debate on the question of whether the DMS is present in the detectable levels in the [K2-18b] The atmosphere, because increased precision has not helped to detect it with higher importance, “said Jake Taylor at the University of Oxford.

In another blow to the affirmations of a biosignature, HU and his team found that for certain atmospheres rich in hydrogen on planets like K2-18B, there are chemical paths to produce DMS without presence of life. “This helps us to reduce molecules can be exclusively a biosignature in exoplanet atmospheres, and it seems that these models exclude the DMS as an exclusive biosignature,” explains Taylor.

However, he adds that other observations with the average JWST infrared instrument, which was used for observations in April, could give us more detailed information, because it targets a different light of light where a DMS characteristic, as well as other complex molecules, could be detectable.

Something on which astronomers can agree, however, is that the planet is rich in water. Hu and his team found solid evidence of the presence of methane and carbon dioxide, which implies the existence of water, says Hu. However, it is still not possible to say if it exists in the form of oceans or as water in the atmosphere, or if it is locked inside the planet, he says.

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