The giant planet, starting 124 light years from Earth, has provided the most powerful evidence that extraterrestrial life could thrive beyond our solar system, astronomers argue.
Observations by the James Webb Space Telescope on the planet, called K2-18 B, appear to reveal the chemical fingerprints of two compounds known to be produced only by life on Earth.
Chemical detection, dimethyl sulfide (DMS), dimethyl disulfide (DMD) are not evidence of foreign biological activity, but can provide answers to the question of whether or not you are alone in the universe.
“This is the most powerful evidence ever for biological activity beyond the solar system,” said Professor Nikuku Madhusdan, an astrophysicist at the University of Cambridge, who led the observations. “We’re very careful. We have to question ourselves both whether the signal is genuine and what it means.”
He added: “Demons from now on, we may look back at this point and realize that it was when the living universe was within reach. This could be a turning point.
Others are more skeptical, leaving questions about whether the overall conditions of K2-18 B are advantageous for life and whether DMS and DMD, which are primarily produced by marine phytoplankton on Earth, can be reliably considered as biosignatures.
K2-18 B in the Leo constellation is nearly nine times larger and orbital than Earth, 2.6 times larger than the star’s habitable zone, and is a cool red dwarf less than half the sun’s. When the Hubble Space Telescope appeared to have found water vapor in the atmosphere in 2019, scientists declared it “the most habitable and known world” beyond the solar system.
The expected water signal was shown to be methane in 2023 in a follow-up observation by Madhusudhan’s team. However, they argued that the profile of the K2-18 B coincided with a vast, deep ocean-covered habitable world. More provocatively, the Cambridge team reported tentative tips for the DMS.
Planets beyond our solar system are far too far away than we can take photos or reach on our robotic spacecraft. However, scientists can probe chemical compositions by estimating their size, density, and temperature, and tracking the way in which they pass through the surface of a host star and measure starlight filtered into the atmosphere. In our most recent observations, the wavelengths absorbed by DMS and DMD appeared to suddenly fall off as K2-18 B wandered in front of the red d star.
“This signal has become strongly and clear,” Madhusdan said. “If we can detect these molecules on habitable planets, this is the first time that it has been able to do that as a species…it’s daunting to see that this is possible.”
Findings published in the Astrophysical Journal Letters suggest concentrations of DM, DMD, or both (their signatures are duplicated). Results are reported at the “three sigma” level, although not at the gold standard for physics discovery.
“There may be processes that don’t know that they are producing these molecules,” Madhusdan said. “But I don’t think there is a known process that can explain this without biology.”
The challenge in identifying other potential processes is that the conditions for K2-18 B remain contested. The Cambridge team prefers ocean scenarios, but others say that data is gas planet or Sea made of magmanot water.
There is a question of whether DMS was brought to the planet by comets. This requires the strength of the bombing that appears to be unbearable.
“Life is one of the options, but it’s one of many,” said Dr. Nora Henni, a chemist at the Institute of Physics at the University of Bern. DMS was present on an ice-free comet. “Before you claim life, you must strictly exclude all other options.”
Others say that measuring the planet’s atmosphere will never produce a smoking gun for the rest of their lives. “Although it is underestimated in this area, technical departments such as intercepted messages from advanced civilizations could be better smoking guns despite the unlikely chance of finding such signals.
Dr. Joe Burstow, a planetary scientist at Open University, also considered detection important, but “my skeptical dialing of any claims relating to life evidence is not because I don’t think other life is there, but because of such profound and important discoveries, I think this latest cross of work is very unthinkable.”
While there is no hope of resolving the debate through close-up observations 120 light years away, Madhusudhan points out that this was not a barrier to the discovery of black holes and other cosmic phenomena.
“In astronomy, the problem is never going to go there,” he said. “We are trying to establish whether the laws of biology are essentially universal. We don’t think, ‘We have to go swimming in the water to catch fish.’ ”
