科學家發現遙遠行星上存在生命的“最有力證據”

Scientists have recently made a significant discovery regarding a distant planet that may harbor life. A research team from Cambridge University has been investigating a planet known as K2-18b, which is located approximately 124 light years away from Earth. This planet is notably larger than our own, measuring two and a half times the size of Earth. The team has detected signs of certain molecules in K2-18b's atmosphere that, on our planet, are typically produced by simple living organisms. This finding marks the second time that chemicals associated with life have been identified in the atmosphere of this planet using the advanced James Webb Space Telescope (JWST). However, the researchers and independent astronomers emphasize the need for further data to validate these results. The lead researcher, Professor Nikku Madhusudhan, expressed optimism about obtaining more conclusive evidence in the near future. He stated, 'This is the strongest evidence yet there is possibly life out there. I can realistically say that we can confirm this signal within one to two years. ' K2-18b is situated at a staggering distance of 700 trillion miles from Earth, making it impossible for humans to travel there within a lifetime. The JWST is equipped with the capability to analyze the chemical composition of the planet's atmosphere by examining the light that passes through it from the small red star it orbits. The Cambridge team has identified the presence of at least one of two molecules associated with life: dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). On Earth, these gases are produced by marine phytoplankton and bacteria. Professor Madhusudhan expressed surprise at the quantity of gas detected during a single observation window, noting, 'The amount we estimate of this gas in the atmosphere is thousands of times higher than what we have on Earth. ' If this association with life is accurate, it could imply that K2-18b is teeming with life forms. He further stated, 'If we confirm that there is life on K2-18b, it should basically confirm that life is very common in the galaxy. ' This discovery is not only significant for science but also for humanity as a whole. If life exists on one planet, it raises the possibility that there could be life on many other planets throughout the universe. Dr. Subir Sarkar, a lecturer in astrophysics at Cardiff University and a member of the research team, mentioned that the findings suggest K2-18b could possess an ocean that might be rich in life, although he cautioned that scientists still do not know for certain. He advised, 'Keep watching this space. ' At this stage, there are numerous uncertainties, and the researchers acknowledge the challenges they face. The current evidence is not robust enough to claim a definitive discovery. To make such a claim, the researchers need to be approximately 99. 99999% certain of their results, which is referred to as a five sigma result. The current findings only reach three sigma, or 99. 7% certainty, which, while impressive, is insufficient to convince the broader scientific community. Even if the Cambridge team achieves a five sigma result, it will not serve as conclusive proof of life on the planet, according to Professor Catherine Heymans of Edinburgh University, who is independent of the research team. She noted, 'Even with that certainty, there is still the question of what is the origin of this gas. ' On Earth, these gases are produced by microorganisms in the ocean, but even with perfect data, it remains uncertain whether the gases on K2-18b have a biological origin. The Cambridge team shares this perspective and is collaborating with other groups to investigate whether DMS and DMDS can be produced by non-living processes in the laboratory. Professor Madhusudhan highlighted that there remains a 0. 3% chance that their findings could be a statistical anomaly. He emphasized the importance of being thorough and meticulous in their research, stating, 'So we want to be really, really thorough, and make more observations, and get the evidence to the level that there is less than a one-in-a-million chance of it being a fluke. ' He believes this goal is achievable within one to two years. Other research teams have proposed alternative, non-living explanations for the data obtained from K2-18b. There is an ongoing scientific debate not only about the presence of DMS and DMDS but also regarding the planet's overall composition. Many researchers infer that K2-18b may have a vast liquid ocean due to the absence of ammonia in its atmosphere, theorizing that the ammonia is absorbed by a large body of water beneath the surface. However, this could also be explained by the presence of a molten rock ocean, which would not support life, according to Professor Oliver Shorttle of Cambridge University. He remarked, 'Everything we know about planets orbiting other stars comes from the tiny amounts of light that glance off their atmospheres. So it is an incredibly tenuous signal that we are having to read, not only for signs of life, but everything else. ' Dr. Nicolas Wogan at NASA's Ames Research Center has proposed yet another interpretation of the data. Both of these alternative interpretations have faced challenges from other groups, who argue that they are inconsistent with the data from the JWST, further complicating the scientific debate surrounding K2-18b. Professor Chris Lintott, a presenter of the BBC's The Sky at Night, expressed admiration for Professor Madhusudhan's team but urged caution regarding their findings. He stated, 'I think we've got to be very careful about claiming that this is a moment in the search for life. We've had such moments before. ' He suggested that this research should be viewed as part of a larger effort to understand what exists in the cosmos. Professor Madhusudhan acknowledges that there is still a significant scientific journey ahead in answering one of the most profound questions in science. However, he remains optimistic that he and his team are on the right path. He concluded, 'Decades from now, we may look back at this point in time and recognize it was when the living universe came within reach. ' The research has been published in The Astrophysical Journal Letters, highlighting the remarkable capabilities of the James Webb Space Telescope in analyzing the atmospheres of planets located hundreds of trillions of miles away.