Artist’s Impression of Exoplanet K2-18b A. Smith/N. Mandusudhan
The quest for extraterrestrial life intensified this year when scientists detected intriguing signals from exoplanets containing molecules associated with life on Earth. Although subsequent attempts to confirm these findings were unsuccessful, exoplanet researchers believe the resulting discussions provided valuable insights for future alien detection efforts.
In April, Nick Madhusudan and his team at the University of Cambridge announced they observed “the first hints of another world, possibly inhabited.” These signals originated from K2-18b, an exoplanet approximately eight times the mass of Earth and located 124 light-years away within its star’s habitable zone, as observed with the James Webb Space Telescope (JWST).
The infrared radiation emitted by K2-18b suggests its atmosphere may contain dimethyl sulfide (DMS), a molecule known to be produced solely by living organisms, particularly marine phytoplankton, here on Earth.
As expected, this discovery generated significant buzz within both media and the scientific community. However, many researchers advised caution, emphasizing that the DMS signal was weak and required additional observations and rigorous analysis for confirmation.
Now, several months later, most astronomers concur that there is currently no evidence of DMS or any biomolecules in K2-18b’s atmosphere. Should they exist, they remain undetectable. “We only know for certain that methane and carbon dioxide are present in the atmosphere of this planet,” explains Lewis Wellbanks from Arizona State University.
Claims of discovering extraterrestrial life were premature, according to Wellbanks. “It’s been shown repeatedly that this information is inaccurate. New observations indicate that those gases are not present,” he asserted.
Yet, the data spike initially attributed to DMS still requires clarification, says Jake Taylor at Oxford University. “We observed a spike—a physical phenomenon. At this point, we still don’t know what it signifies.”
Identifying the molecules responsible for these spikes requires further exploration planned for the JWST next year. Scientists can only ascertain what’s present in a planet’s atmosphere by analyzing the starlight filtering through it during the planet’s transit across its host star. This occurs four times each Earth year.
Despite the controversy surrounding this discovery, Taylor notes it also fostered positive outcomes. “This has been a significant learning experience for the entire exoplanet community. We are reassessing our definitions and statistical methods, which has been tremendously beneficial,” he states.
“This experience teaches us to calibrate our expectations,” says Wellbanks. “It’s a reminder that relying on data manipulation to validate a claim is challenging. As one wise person noted, there are lies, damned lies, and statistics. This whole DMS saga falls into that category.”
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Source: www.newscientist.com
