Potentially habitable oceanic world K2-18b turns out to be an extremely inhospitable gas planet An exoplanet called K2-18b is considered a “good” place to look for extraterrestrial life, but new research suggests it is likely made of hot gas. There is. A distant planet recently named as a potential search for extraterrestrial life is actually a very inhospitable place, astronomers say. Experts say it’s probably not a hard surface. In 2015, a planet called K2-18b was discovered 110 light years from Earth. According to preliminary estimates, it is a super-Earth or mini-Neptune with eight times the mass of Earth In 2019, astronomers discovered evidence of water vapor on the planet. Because K2-18b is in the star’s habitable zone (a region where water can exist in liquid form on the planet’s surface), this suggests that K2-18b may be an oceanic or high-sea world. doing. Hopes were boosted after a 2023 study found evidence of dimethyl sulfide, an organic compound produced only on Earth by organisms such as marine phytoplankton. But recently, Nicholas Vaughan and colleagues at NASA’s Ames Research Center in California reanalyzed his K2-18b using data from the James Webb Space Telescope (JWST). They concluded that this planet was highly unlikely to be a habitable oceanic world. They say the amounts of methane and carbon dioxide detected by JWST indicate that the planet is not a habitable super-Earth with oceans and an ocean floor, but a gas-rich mini-Neptune with no special surface. It is said to be suggesting. If K2-18b were an oceanic or “Haian” planet, these gases would simply be broken down by a chemical process called photodissociation. The researchers write in their paper that there are two possible options: the planet could be an “oceanic world populated by methane-producing organisms” that produce methane, or “or a normal planet with no noticeable surface.” It is likely to be one of the mini-Neptunes. Fewer assumptions are required. ” “In general, we prefer the mini-Neptune option,” says the expert. “And in either case, trace amounts of dimethyl sulfide could simply be a false signal,” said Thomas Beatty of the University of Wisconsin-Madison. It emphasizes that any claims made about this must be subject to rigorous testing. . Simulations show Earth could be ejected from the solar system if the star passes by “It will be very difficult to get real confirmation that there is life on Earth,” he says. “We have to eliminate all non-life options so that the most likely outcome is life.” Results from other recent studies on K2-18b suggest a slightly different possibility . K2-18b could be a huge world with an ocean containing magma instead of water, and the emergence of life is equally unlikely. If dimethyl sulfide were found in more reliable quantities in the future, Vaughn and colleagues said, it would be “very difficult to explain its existence” even if Earth was not a habitable oceanic world. Pointed out. Further observations from JWST will help determine exactly which scenario is most likely.

Many of the mini-Neptunes studied have densities potentially suitable for the presence of vast oceans of liquid water (giant planets). The presence of CO2 and the simultaneous absence of ammonia (NH3) in the atmosphere has been proposed as the “fingerprint” of such a world. Her JWST observations of K2-18b, a typical giant planet, showed atmospheric carbon dioxide and low NH3 levels of less than 100 ppm. Therefore, it was hypothesized that this planet may have an ocean with liquid water. At the same time, climate modeling shows that many of these mini-Neptunes, including K2-18b, are likely too hot to support liquid water. The authors of this project sought to find a solution to the discrepancy between observations and climate modeling by studying the influence of magma oceans on mini-Neptune’s atmospheric chemistry. The decomposition of NH3 in the atmosphere is a natural consequence of the high solubility of nitrogen in magma under reducing conditions, the very conditions that exist when thick hydrogen shells interact with the molten planetary surface. It has been found. The magma ocean model reproduces the spectrum of K2-18b from JWST data with an accuracy of ±3Ï, providing an explanation for current observations as convincing as the existence of a liquid water ocean on Earth. . Among the spectral regions where the analysis allows us to rule out the magma ocean model is a region above 4 μm characterized by a predominance of CO2 and CO. The magma ocean model shows systematically lower CO2/CO ratios compared to data from “free chemistry” analyses. Therefore, by looking deeper into this spectral region, we may be able to distinguish between mini-Neptune’s magma and liquid water oceans.