Astronomers have detected the most promising signs yet of a possible biosignature outside the solar system. The most likely reason (when combined with other observation) for seeing 1000 times more of the chemical DMS would be that exoplanet K2-18B is an ocean planet teeming with life. This ocean filled with life is causing the chemical DMS to saturate the atmosphere.
Researcher are now 99.7% certain of the detections of the key chemical signature. We need to confirm with another 24 hours of James Webb Space Telescope. If those observations were also confirmed then we would be 99.99994% certain the DMS chemical signature is good.
If we become 99.99994% certain there is DMS then scientists are convinced that DMS is there and then it needs to be explained. The leading reason is that there is the mother lode of ocean with high concentrations of marine phytoplankton on an exoplanet 120 light years away OR there is some unknown exoplanet geology or planetary mechanism that does not exist on earth that makes DMS instead of phytoplankton. Like some weird volcanos spewing DMS from a different exoplanet magma composition.
So they will first make the 24 hours of additional observations with the James Webb Telescope. They will make the theoretical and experimental work to determine whether DMS and DMDS can be produced non-biologically at the level currently inferred.
There is now a third different instrument now show that there is the DMS life signature.
Using data from the James Webb Space Telescope (JWST), the astronomers, led by the University of Cambridge, have detected the chemical fingerprints of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS), in the atmosphere of the exoplanet K2-18b, which orbits its star in the habitable zone.
On Earth, DMS and DMDS are only produced by life, primarily microbial life such as marine phytoplankton. While an unknown chemical process may be the source of these molecules in K2-18b’s atmosphere, the results are the strongest evidence yet that life may exist on a planet outside our solar system.
The observations have reached the ‘three-sigma’ level of statistical significance – meaning there is a 0.3% probability that they occurred by chance. To reach the accepted classification for scientific discovery, the observations would have to cross the five-sigma threshold, meaning there would be below a 0.00006% probability they occurred by chance.
The researchers need between 16 and 24 hours of follow-up observation time with JWST may help them reach the all-important five-sigma significance.
Earlier observations of K2-18b — which is 8.6 times as massive and 2.6 times as large as Earth, and lies 124 light years away in the constellation of Leo — identified methane and carbon dioxide in its atmosphere. This was the first time that carbon-based molecules were discovered in the atmosphere of an exoplanet in the habitable zone. Those results were consistent with predictions for a ‘Hycean’ planet: a habitable ocean-covered world underneath a hydrogen-rich atmosphere.
Astronomers analyze the light from its parent star as the planet transits, or passes in front of the star as seen from the Earth. As K2-18b transits, JWST can detect a drop in stellar brightness, and a tiny fraction of starlight passes through the planet’s atmosphere before reaching Earth. The light pass throuhg the planet’s atmosphere changes the stellar spectrum that astronomers can use to determine the constituent gases of the exoplanet’s atmosphere.
The earlier weaker detection of DMS was made using JWST’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph) instruments, which together cover the near-infrared (0.8-5 micron) range of wavelengths. The new, independent observation used JWST’s MIRI (Mid-Infrared Instrument) in the mid-infrared (6-12 micron) range.
Three instruments are detecting DMS.
The concentrations of DMS and DMDS in K2-18b’s atmosphere are far higher than on Earth, where they are generally below one part per billion by volume. On K2-18b, they are estimated to be thousands of times stronger – over ten parts per million.
The most likely scenario is that K@-18B is Hycean world (ocean covered) with an ocean that is teeming with life is the scenario that best fits the data we have.
Source: Next Big Future / Digpu NewsTex