A new study from the University of California, Riverside (UCR) has called into question recent reports suggesting that NASA’s James Webb Space Telescope (JWST) had discovered signs of life on a distant planet. However, the researchers also provide insights into how the telescope might confirm the presence of a life-produced gas in the future, keeping the hope for discovering extraterrestrial life alive.
The study, published in the Astrophysical Journal Letters, centers on the exoplanet K2-18b, which orbits a star approximately 120 light-years away from Earth. In 2023, a Cambridge team reported the detection of methane, carbon dioxide, and a tentative signal of dimethyl sulfide (DMS) in the planet’s atmosphere using JWST data. DMS is a gas produced by ocean phytoplankton on Earth and is considered a potential biosignature, making its possible presence on K2-18b particularly exciting.
Challenging the DMS Detection
To determine whether enough DMS could accumulate to detectable levels on K2-18b, the UCR researchers employed computer models that account for the physics and chemistry of DMS and the planet’s hydrogen-rich atmosphere. They found that the DMS signal from the JWST data was not very strong and significantly overlapped with methane, making it difficult to distinguish between the two gases.
“The signal strongly overlaps with methane, and we think that picking out DMS from methane is beyond this instrument’s capability,” said UCR project scientist and paper author Shang-Min Tsai. “What was icing on the cake, in terms of the search for life, is that last year these researchers reported a tentative detection of dimethyl sulfide, or DMS, in the atmosphere of that planet, which is produced by ocean phytoplankton on Earth.”
Despite the challenges in detecting DMS on K2-18b, the researchers believe it is possible for the gas to accumulate to detectable levels if plankton or some other life form produces 20 times more DMS than is present on Earth. This finding highlights the potential for discovering signs of life on exoplanets, even if the biosignatures differ from those most abundant on our planet.
Hope for Future Discoveries
Although the recent study challenges the initial reports of DMS detection on K2-18b, the researchers remain optimistic about the possibility of discovering signs of life on exoplanets in the near future. The JWST is scheduled to use an instrument better suited for detecting infrared wavelengths in the atmosphere later this year, which could provide a definitive answer about the presence of DMS on K2-18b.
“The best biosignatures on an exoplanet may differ significantly from those we find most abundant on Earth today. On a planet with a hydrogen-rich atmosphere, we may be more likely to find DMS made by life instead of oxygen made by plants and bacteria as on Earth,” said UCR astrobiologist Eddie Schwieterman, a senior author of the study.
The researchers emphasize the importance of continuing to explore the cosmos for signs of life, despite the complexities and challenges involved in searching for biosignatures on distant planets. “Why do we keep exploring the cosmos for signs of life? Imagine you’re camping in Joshua Tree at night, and you hear something. Your instinct is to shine a light to see what’s out there. That’s what we’re doing too, in a way,” Tsai said.
As the search for life beyond Earth continues, studies like this one help refine our understanding of potential biosignatures and guide future observations. By challenging initial findings and proposing new ways to detect signs of life, researchers are paving the way for groundbreaking discoveries that could answer one of the most profound questions in science: Are we alone in the universe?
The detection of life on an exoplanet would have far-reaching implications, not only for our understanding of the prevalence of life in the universe but also for our place within it. As technology advances and our knowledge of exoplanets expands, we inch closer to potentially discovering the first evidence of extraterrestrial life, forever changing our perspective on the cosmos and our role within it.
While the journey to finding definitive proof of life beyond Earth may be long and filled with challenges, studies like this one demonstrate the unwavering dedication of scientists to pursue this monumental goal. As we continue to explore the vast expanse of space, each new discovery, whether confirming or challenging previous findings, brings us one step closer to unraveling the mysteries of the universe and our place within it.
Keyword: exoplanet biosignatures
