You may have heard rumors about a mysterious exoplanet called K2-18 b. Located 120 light-years away from Earth, this distant world has been the subject of much speculation and excitement in recent years, especially following the launch of the James Webb Space Telescope (JWST) in 2021.
The JWST is the most powerful space telescope ever built and can detect the faint infrared light of distant stars and planets. One of its main goals is to study the atmospheres of exoplanets – planets orbiting other stars – and look for signs of life, such as oxygen, methane or other organic molecules.
K2-18 b is one of the top targets for JWST because it is a rare type of exoplanet known as a ‘hycean’ world. Hycean planets are larger and more massive than Earth, but smaller and less dense than gas giants like Jupiter. They have a thick, hydrogen-rich atmosphere and deep oceans with liquid water on their surfaces. These conditions could make them ideal habitats for life, even more so than Earth-like planets.
But has JWST found evidence of life on K2-18 b yet? That’s what some people believe, based on a cryptic statement made by British astronaut Tim Peake in 2020. In an interview with The Sun, Peake said:
“The James Webb telescope may have already found this [alien life]…it’s just that they don’t want to release or confirm these results until they’re completely sure, but we have found a planet that appears to be giving off strong signals of biological life.”
Peake did not name the planet he was referring to, but many assumed it was K2-18 b, as it was one of the most promising candidates for life at the time. Peake’s statement sparked a lot of excitement and curiosity among astrobiologists and space enthusiasts, who wondered whether he had prior knowledge or was simply speculating.
But before you get too excited, you should know that there has been no official confirmation or announcement from NASA or ESA (the agencies behind JWST) that they have found life on K2-18 b or any other exoplanet. In fact, JWST hasn’t even observed K2-18 b yet, as it is still being tested and calibrated in orbit.
According to Knicole Colon, deputy project scientist for JWST at NASA’s Goddard Space Flight Center, JWST has not found definitive evidence of life on an exoplanet. She said Ars Technica:
“It is expected that JWST observations could lead to the first identification of potential biosignatures that could make the habitability of a given exoplanet more or less likely.”
“Future missions will be needed to definitively determine the habitability of an exoplanet.”
In other words, JWST will only be able to detect some clues that may indicate the presence or absence of life on an exoplanet, but will not be able to conclusively prove it. More observations and analyzes from other telescopes and missions will be needed to confirm or rule out the existence of extraterrestrial life.
So what can we expect from JWST when it comes to Q2-18 b? Colon said JWST will observe K2-18 b in 2024, as part of its Early Release Science program. This program will highlight some of JWST’s early scientific achievements and demonstrate its capabilities to the scientific community and the public.
JWST will use its Near-Infrared Spectrograph (NIRSpec) instrument to measure the spectrum of light emanating from K2-18 b as it passes in front of its host star. This will reveal the chemical composition and structure of the atmosphere and possibly detect some biosignatures.
However, Colon cautioned that detecting biosignatures on K2-18 b will not be easy, as the hydrogen-rich atmosphere makes it more difficult to see through than Earth-like atmospheres. She said:
“Hydrogen-dominated atmospheres are more difficult to observe with JWST because they are more opaque than lower average molecular weight atmospheres (such as Earth’s atmosphere).”
“This means there are fewer wavelength regions where we can look deeper into the atmosphere and potentially detect biosignatures.”
She also noted that K2-18 b is not a perfect analog for Earth, because it is much larger and hotter than our planet. It receives about four times more radiation from its star than Earth does from the Sun, which could affect its climate and chemistry.
Therefore, even if JWST detects certain biosignatures on K2-18 b, such as oxygen or methane, they may not necessarily indicate life. They can also be produced by non-biological processes, such as photochemistry or volcanism.
Colon said:
“Detecting biosignatures on exoplanets is not a simple yes or no answer. It requires careful interpretation of the data and comparison with models and observations of other planets (including our own).
“Ultimately, we need to build a statistical sample of exoplanets with different characteristics and look for trends and outliers that could indicate the presence or absence of life.”
So while K2-18b remains a fascinating and promising world to explore, we shouldn’t jump to conclusions based on rumors or speculation. JWST will soon give us a glimpse into the atmosphere, but it will take more time and effort to determine whether it is actually habitable or inhabited.
Until then, we can only wonder and hope that we are not alone in the universe.
