Did the James Webb Space Telescope spot indicators of life on a distant planet? On September 11, 2023, NASA announced that Webb made some thrilling discoveries whereas observing an exoplanet known as K2-18 b. They stated the planet has methane and carbon dioxide in its environment, which signifies it is perhaps a Hycean world, one with a deep hydrogen environment and world water ocean. However the extraordinary information is that Webb discovered hints of a molecule known as dimethyl sulfide (DMS). On Earth, solely life produces dimethyl sulfide, equivalent to micro organism and phytoplankton in oceans.
Does that imply Webb has discovered indicators of life on exoplanet K2-18 b? Effectively, first, the discovering of dimethyl sulfide must be confirmed. After which, scientists should be taught extra in regards to the exoplanet. Whereas it’s within the habitable zone of its star, its setting may nonetheless be unfavorable to life. As NASA said, it could have a hostile setting on account of its energetic star, or its ocean can also be too scorching to be liveable. Nonetheless, the brand new discovery is tantalizing.
Whereas learning the exoplanet K2-18 b, @NASAWebb hinted at a detection of dimethyl sulphide (DMS). On Earth, this molecule is simply produced by microbial life. As a result of the detection must be confirmed, the staff will observe up with further observations. https://t.co/lYRNSVgI0M pic.twitter.com/Ui3c1fDbSf
— NASA Exoplanets (@NASAExoplanets) September 11, 2023
Extra about K2-18 b
K2-18 b is what scientists name a sub-Neptune or mini-Neptune. The exoplanet is 2.6 instances bigger and eight.6 instances extra huge than Earth. The brand new knowledge from Webb present that the exoplanet can also be possible a Hycean world. And in contrast to many sub-Neptunes, scientists say that Hyceans could also be liveable. On this occasion, liveable means the situations might be proper for all times to type. It doesn’t imply that we’re planning to ship earthly life to the exoplanet.
The Webb discovery can also be the first time that astronomers have found carbon molecules within the environment of a planet in its star’s liveable zone.
The brand new analysis paper has been accepted for publication in The Astrophysical Journal Letters. Within the meantime, a draft model of the paper is available from ESA.
A Hycean world with an ocean?
K2-18 b orbits within the liveable zone of a red dwarf star about 124 light-years from Earth, within the constellation Leo the Lion. The liveable zone is the area round a star the place temperatures may permit liquid water to exist. To be clear, this doesn’t show that K2-18 b is definitely liveable, though the brand new findings from Webb help that it’s doable.
Additionally, Hyceans are a more moderen recognized class of exoplanet, and there’s nonetheless lots that we don’t learn about them. Not like most sub-Neptunes, nevertheless, they are able to have strong surfaces beneath their deep hydrogen atmospheres. And beneath the environment, a worldwide water ocean. They might nonetheless be hotter than Earth, however maybe not too scorching for lifetime of some variety.
The invention of methane (CH4) and carbon dioxide (CO2) – and a scarcity of ammonia – help the speculation that K2-18 b is a Hycean planet, the researchers stated. Lead creator Nikku Madhusudhan, an astronomer on the College of Cambridge, said that:
Our findings underscore the significance of contemplating various liveable environments within the seek for life elsewhere. Historically, the seek for life on exoplanets has centered totally on smaller rocky planets, however the bigger Hycean worlds are considerably extra conducive to atmospheric observations.
The researchers stated that K2-18 b possible has a mantle of high-pressure ice, just like Neptune. The Webb outcomes help the opportunity of a planet-wide ocean on the floor, though it’s nonetheless doable that the planet is simply too scorching. Or no less than too scorching for the ocean to be liveable. Solely further observations will assist astronomers decide the precise situations.
Webb detects doable biosignature
The presence of methane, carbon dioxide and a doable ocean are definitely attention-grabbing on their very own after all. However Webb additionally probably detected one thing much more tantalizing within the environment of K2-18 b: dimethyl sulfide (DMS). Dimethyl sulfide is an natural sulfur compound. On Earth, it’s only produced naturally by organic processes from organisms equivalent to micro organism and phytoplankton in marine environments.
That is nonetheless tentative, nevertheless. Whereas there’s a doable detection, it’s much less strong than the detections of methane and carbon dioxide. The paper stated:
The potential inference of DMS is of excessive significance as it’s recognized to be a sturdy biomarker on the Earth and has been extensively advocated to be a promising biomarker for exoplanets.
Total, we discover CH4 and CO2 to be our most assured detections, adopted by DMS, with the abundance estimates reported above. Whereas our outcomes present essential first insights into the chemical composition of K2-18 b, upcoming observations will be capable of confirm our current findings.
These findings help the Hycean nature of K2-18 b and the potential for organic exercise on the planet.
Madhusudhan said:
The opportunity of DMS within the environment is very promising, however we’re planning to take one other look to robustly set up its presence.
Most detailed spectrum of a liveable zone sub-Neptune
Webb’s observations are essentially the most detailed but of a sub-Neptune within the liveable zone. Co-author Subhajit Sarkar of Cardiff College said:
Though this sort of planet doesn’t exist in our solar system, sub-Neptunes are the commonest sort of planet recognized thus far within the galaxy. We have now obtained essentially the most detailed spectrum of a liveable zone sub-Neptune up to now, and this allowed us to work out the molecules that exist in its environment.
Savvas Constantinou of the College of Cambridge added:
These outcomes are the product of simply two observations of K2-18 b, with many extra on the way in which. This implies our work right here is however an early demonstration of what Webb can observe in habitable-zone exoplanets.
Future observations with Webb
In fact, now we wish to know if Webb will likely be doing any follow-up observations. The reply is sure. The staff will use the telescope’s MIRI (Mid-Infrared Instrument) spectrograph to additional analyze the planet’s environment. As Madhusudhan said:
Our final purpose is the identification of life on a liveable exoplanet, which might rework our understanding of our place within the universe. Our findings are a promising step towards a deeper understanding of Hycean worlds on this quest.
Backside line: NASA’s Webb telescope regarded on the sub-Neptune exoplanet K2-18 b. It discovered methane, carbon dioxide, a doable ocean, and even … possibly … a biosignature.
Source: Carbon-bearing Molecules in a Possible Hycean Atmosphere
Read more: Hycean planets might be habitable ocean worlds
Read more: Super-Earth, mini-Neptune or sub-Neptune?
