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Astronomers Detect Potential Biosignature on Distant Exoplanet K2-18b
In a groundbreaking discovery, astronomers have identified a significant indicator of potential life on a far-off exoplanet. New findings suggest the presence of a molecule possibly linked to living organisms on K2-18b, a planet orbiting a star outside our solar system.
K2-18b Classified as a “Hycean” World
Scientists propose that exoplanet K2-18b is a “Hycean planet.” This classification suggests it possesses substantial quantities of dimethyl sulfide (DMS), a molecule on Earth exclusively produced by living organisms, primarily phytoplankton in marine environments. This compelling observation is detailed in a recent scientific report.
Dimethyl Sulfide Detected in Exoplanet’s Atmosphere
The exoplanet K2-18b, approximately eight times larger than Earth and situated 124 light-years away, exhibits signs of dimethyl sulfide (DMS). This discovery is based on a study published in the Astrophysical Journal on Wednesday.
“This marks a revolutionary moment in our search for extraterrestrial life,” stated Dr. Nikku Madhusudhan, astronomer at the University of Cambridge and lead author of the study, during a press briefing as reported by NPR.
“These initial indications represent our first glimpse into an alien world that could potentially support life,” he asserted.
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Dimethyl sulfide, an organic compound comprising sulfur, carbon, and hydrogen, is a natural byproduct of phytoplankton. It’s also found in certain bacteria, such as those involved in beer production, and is commonly detected above Earth’s oceans.
James Webb Space Telescope Confirms DMS Presence
Madhusudhan and his research team initially measured atmospheric dimethyl sulfide on K2-18b in 2023. Subsequent observations and tests conducted last year using the powerful James Webb Space Telescope (JWST) corroborated the significant presence of this molecule.
The signals indicating this potential biosignature were so robust that researchers faced challenges in excluding them during other analyses. Dimethyl sulfide levels were measured to be 1,000 times greater than levels typically found on Earth, according to the study.
“It was an astonishing finding,” Madhusudhan commented at the press event. “We invested considerable effort in verifying the signal and excluding any potential contamination.”
“Hycean” World Theory Strengthened by Findings
K2-18b was already known to contain water vapor. The recent detection of dimethyl sulfide reinforces the “Hycean world” hypothesis proposed by researchers in 2021, suggesting K2-18b fits this planetary classification.
Dr. Madhusudhan coined the term “Hycean” in 2021 to describe a subtype of exoplanets known as “sub-Neptunes.” These celestial bodies are characterized by liquid oceans and hydrogen-rich atmospheres, characteristics that researchers initially believed applied to K2-18b.
James Webb Space Telescope readings from 2023 enabled Madhusudhan’s team to verify the presence of several molecules predicted by their “Hycean” model. These included hydrogen, methane, and other carbon-based compounds, alongside the initial discovery of dimethyl sulfide.
Spectroscopic Analysis Using JWST
To obtain these atmospheric measurements, scientists utilize the James Webb Space Telescope to observe light from the host star as it filters through the exoplanet’s atmosphere. This occurs as the sub-Neptune traverses in front of its star from Earth’s vantage point.
Different elements within the atmosphere absorb and emit specific wavelengths of light, creating a spectrum. By analyzing these spectral patterns as the planet transits its star, scientists can determine the atmospheric composition and identify potential biosignatures.
Confirmation and Further Research Needed
Despite the compelling measurements indicating the presence of life-related elements, some scientists emphasize the need for additional data and independent verification before a definitive conclusion about life on K2-18b can be reached.
“This discovery is significant,” noted Stephen Schmidt, planetary scientist at Johns Hopkins University, in an interview with the New York Times. “It’s a promising indication. However, we cannot yet definitively conclude that the planet is habitable.”
“Without more direct evidence, it’s not yet a definitive proof of life,” remarked Christopher Glein, planetary scientist at Southwest Research Institute in San Antonio, to the same publication.
Mans Holmberg, a researcher at the Space Telescope Science Institute and participant in the study, urged fellow astronomers to conduct independent analyses of the collected data, as reported by NPR.
“Investigating phenomena of this nature necessitates a collaborative community effort,” Holmberg emphasized.
“It’s crucial to exercise caution. Claims of life beyond Earth require substantial evidence, and we are not at that stage yet,” he concluded.
Discovery and Characteristics of K2-18b
K2-18b was initially detected in 2015 by NASA’s Kepler mission. It was determined to reside within the “habitable zone” or “Goldilocks zone” of its star, where temperatures are conducive to liquid water, considered a fundamental prerequisite for life.
While K2-18b is approximately eight times the size of Earth, it possesses a much shorter orbital period, completing one orbit around its host star in only 33 Earth days.