Khaberni - Three years into its mission, the James Webb Space Telescope has advanced the search for extraterrestrial life more than any previous device, according to Live Science. Over the past two years, there has been a heated debate among alien scientists about the James Webb Space Telescope JWST, which targets planet K2-18b, located about 120 light-years from Earth. There is no doubt that the planet itself is real. However, its surface conditions, and the likelihood of life on it, remain a matter of debate.
"The smell of the sea"
A team of researchers, who have studied planet K2-18b using the James Webb Space Telescope over the past few years, claim to have detected signs of dimethyl sulfide DMS, a foul-smelling compound known on Earth as "the smell of the sea," which is known to be produced only by living phytoplankton that breathe. The research team first reported hints of DMS in the atmosphere of planet K2-18b in 2023, followed by the publication of several research papers since then.
Questionable modeling
However, external researchers remain skeptical about this alleged discovery of DMS, warning that the researchers' discovery relies on questionable data modeling and does not meet the required level for a new scientific discovery. The issue can only be settled through further observation of the planet.
But what is certain is that the James Webb Space Telescope's powerful infrared vision gives humanity the best chance ever to find life beyond Earth.
Atmosphere and water
Eddie Schwieterman, Assistant Professor of Astrobiology at the University of California, who studies the habitability of exoplanets using the James Webb Space Telescope, said it is a given in the search for extraterrestrial life that where there is an atmosphere, there can be water on the planet's surface, and where there is flowing water, life can exist. For the first time, the James Webb Space Telescope sheds light on these extraterrestrial atmospheres.
To detect evidence of an atmosphere around an exoplanet, scientists must wait for a transit - the moment a planet passes in front of its parent star, forcing the star's light to shine through the planet's atmosphere as seen from our perspective on Earth. In the case of planet K2-18b, for example, this occurs every 33 days.
For example, Victoria Meadows, Professor of Astronomy at the University of Washington and Director of the Graduate Program in Astrobiology, said: If the James Webb Space Telescope can capture a spectrum of a planet showing high levels of methane and carbon dioxide absorption in its atmosphere, this may indicate the existence of a habitable Earth-like world in the Archean era (from about 4 billion to 2.5 billion years ago), when primitive microbes were breaking down carbon dioxide and releasing huge amounts of methane. The tricky part is proving the existence of these conditions on a planet trillions of miles away.
Data conundrum
After revealing a promising biosignature, the challenge becomes proving that it cannot be explained by a geological process, such as volcanic activity. Then, scientists must prove that their discovery meets the statistical significance required - a meticulous job that requires repeated observations of the planet and verification by independent researchers using their own data models.
Rene Doyon, Professor at the University of Montreal and the principal investigator on the Near-Infrared Camera and Slit Spectrograph NIRISS device associated with the James Webb Space Telescope, stated, "Webb's data is extremely complex. Researchers have published results that are not always consistent." Depending on who is performing the data reduction, a different answer is obtained. In other words, the early studies of planet K2-18b have been scrutinized. Despite the initial detection of DMS in two studies conducted by a team led by the University of Cambridge, external experts have not yet been able to verify the result when looking at the same observations using different data models.
Three sigma level
The discovery of DMS has only reached a three-sigma level of statistical significance, which is much lower than the required five-sigma level. (A three-sigma level means about 3 out of 1000 chances that it is just a coincidence, while a five-sigma value means there is a 1 out of 3.5 million chance that it is a coincidence).
Niko Madhusudan, Professor of Astrophysics at Cambridge and the principal investigator of the DMS studies, said that this is not a reason to dismiss K2-18b as a candidate for a habitable world "teeming with microbial life," explaining that only when more data is obtained "can we confirm what we see."
Promising sign of life
Schwieterman believes that it is "premature" to announce the discovery of DMS on K2-18b, due to the questionable statistical significance. However, he agrees that DMS is a promising sign of life, and that the James Webb Space Telescope should continue the search for it in other potentially habitable oceanic worlds.
Hitting the target
The telescope's search list includes some usually suspected planets, such as the TRAPPIST-1 system - the only star system more studied than the solar system, containing seven rocky planets, at least three of which could be within the star's habitable zone.
So far, the James Webb Space Telescope has not been able to confirm the presence of an atmosphere around any of the three planets that may be habitable: TRAPPIST-1B, C, or D. However, a study published in the Astrophysical Journal Letters provided preliminary evidence that there might be a nitrogen-based atmosphere around TRAPPIST-1E, making it one of the most promising candidates to be an Earth-like planet outside the solar system.
Oxygen sensitivity
One of the major gaps is oxygen. While the gas makes up about 21% of Earth's atmosphere and represents a strong biosignature, Meadows said, "The James Webb Space Telescope cannot detect oxygen."
Upcoming telescopes could help address this. For example, Meadows mentioned that the Extremely Large Telescope - a powerful telescope operating in near-infrared/optical wavelengths, currently under construction in Chile and expected to see first light in 2029 - will be more sensitive to oxygen and water in planetary atmospheres than the James Webb Space Telescope. It will also be able to look at the surfaces of rocky planets - closer to the places where life and its byproducts might be found, unlike the high upper atmospheres that fall within the scope of the James Webb Space Telescope.
Worlds suitable for human habitation
In the future, the recently announced Habitability Worlds Observatory by NASA will conduct a census of planets orbiting Sun-like stars near our Solar Neighborhood. Using visible light and infrared analysis with ultraviolet fingerprints, this powerful observatory can confirm the presence of atmospheres around dozens of Earth-like worlds. However, there is currently no planned launch date
