from
https://www.pcmag.com/news/james-webb-telescope-spots-evidence-of-plankton-living-on-alien-ocean-planet

James Webb Telescope Spots Evidence of Plankton Living on Alien Ocean Planet
The molecule dimethyl sulfide naturally occurs from phytoplankton on
Earth. Now the James Webb Space Telescope has detected the molecule's
emissions on an exoplanet called K2-18 b.

Michael Kan
By Michael Kan
September 12, 2023
Illustration of K2-18 bIllustration of K2-18 b (Credits: Illustration:
NASA, CSA, ESA, J. Olmsted (STScI), Science: N. Madhusudhan, Cambridge
University)
NASA’s James Webb Space Telescope has spotted evidence of potential life
on a hydrogen-rich ocean planet based 120 light-years away.

The planet is called K2-18 b and it orbits a dwarf star in the so-called
“habitable zone,” a distance where conditions might be right for life to
exist. The space telescope recently analyzed the light emitted from the
planet to discern its chemical composition.

According to NASA, the findings reveal the presence of “carbon-bearing
molecules including methane and carbon dioxide,” which are all building
blocks to life on our own planet. In addition, the telescope may have
detected the presence of a molecule called dimethyl sulfide (DMS) in the
planet’s atmosphere.

“On Earth, this is only produced by life. The bulk of the DMS in Earth’s
atmosphere is emitted from phytoplankton in marine environments,” NASA
noted.

the spectrum of the planet
(Credit: NASA)
The space agency will need to observe K2-18 b more to validate the
findings. But if true, it could mean a plankton-like organism—which on
Earth act as a crucial food source for other marine life—is present on
the alien world.

However, K2-18 b is quite different from Earth. To start, it's about 8.6
times larger. The data from the James Webb Space telescope also suggests
K2-18 b is a hydrogen-rich world covered with an ocean surface, making
it a “Hycean exoplanet.” That said, it’s possible the planet’s surface
is too hot for life, or for it to sustain a liquid ocean, NASA added.

“The planet's large size — with a radius 2.6 times the radius of Earth —
means that the planet’s interior likely contains a large mantle of
high-pressure ice, like Neptune, but with a thinner hydrogen-rich
atmosphere and an ocean surface,” the space agency said. (In contrast,
Earth's atmosphere is made up mostly of nitrogen and oxygen.)

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The space telescope was able to discern the planet’s chemical
composition by taking a spectrum, which involves dissecting the emitted
light from K2-18 b’s atmosphere. Although other telescopes have taken
spectrums of K2-18 b before, James Webb features more powerful sensors,
which allowed astronomers to gather more data of the planet’s atmosphere.

"These results are the product of just two observations of K2-18 b, with
many more on the way,” University of Cambridge astronomer Savvas
Constantinou told NASA. “This means our work here is but an early
demonstration of what Webb can observe in habitable-zone exoplanets.”