Have astronomers found extraterrestrial life on a distant planet? Here's the discovery
The strongest yet indication of extraterrestrial life – in the form of organically produced chemicals, not an alien civilization – may have been found on a giant exoplanet 124 light-years from Earth, researchers announced in a new study on April 17.
Atmospheric analysis of K2-18b, a planet a bit smaller than Neptune, has revealed two biologically produced compounds from the same chemical family, dimethyl sulfide and dimethyl disulfide.
Though the results aren’t conclusive, the findings are significant because the compounds are made by biological activity, or actions by living organisms, researchers said. On Earth, the two compounds are produced by microbes found in marine algae.
While more research is needed, “It’s the first time humanity has seen potential biosignatures on a habitable planet,” said Nikku Madhusudhan, an astrophysicist at the University of Cambridge in England and one of the study's authors.
What's also remarkable is not just the compounds themselves, but how they were discovered: by a telescope in space.
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What – and where – is the exoplanet K2-18b?
K2-18b is an exoplanet, a planet outside our solar system. It orbits the star K2-18 – also known as EPIC 201912552 – a red dwarf star in the constellation Leo. The exoplanet was discovered in 2015 by NASA's Kepler space telescope and is one of two orbiting K2-18.
The Webb telescope found carbon-bearing molecules, including methane and carbon dioxide, in September 2023. That discovery suggested that K2-18b could be "a Hycean exoplanet, one with the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface," according to NASA.
How K2-18b compares to Earth
K2-18b is about 8.6 times more massive than Earth. It orbits its sun in what's known as a habitable zone (also called the Goldilocks zone) which means its temperature could be warm enough for it to have liquid water.
"Conditions might be just right ‒ not too hot, not too cold ‒ for life," NASA says.
How did a telescope discover gases on K2-18b?
Researchers used infrared cameras aboard the James Webb Space Telescope to analyze light passing through K2-18b's atmosphere as it was moving in front of its star.
The telescope was able to detect some starlight being absorbed into the planet's atmosphere. That left clues for astronomers to determine the gases in the atmosphere.
The analysis helped identify dimethyl sulfide and dimethyl disulfide by their specific chemical molecules, based on the wavelengths of light they absorbed when the planet's atmosphere was illuminated.
The Webb telescope was launched on Dec. 25, 2021. It orbits the sun at a location called the second Lagrange point, at a distance of about 1 million miles from Earth.
How significant is the discovery?
If dimethyl sulfide and dimethyl disulfide are in K2-18b's atmosphere, and if they're from biological activity, "it would represent a groundbreaking moment in the search for extraterrestrial life," says the journal Nature.
However, some skeptics say it's questionable whether the planet has water. Technology website Ars Technica cited a Cornell University study that said K2-18b "doesn't reflect enough light back into space to keep from boiling away any oceans it tries to form."
Ars Technica also noted that the Webb researchers found no sign of clouds on K2-18b, which is significant because, as the researchers reported, "A cloud-/haze-free atmosphere would render the surface too hot to be habitable and/or have water in a supercritical state."
That doesn't prove that clouds don't exist there, "but it certainly doesn't help the case," Ars Technica said.
The Webb telescope observations could have occurred by chance or could be the result of previously unknown chemical processes at work on K2-18b. For that reason, the researchers say an additional 16 to 24 hours of follow-up analysis with Webb could help them reach a more definitive conclusion, Paste BN reported.
CONTRIBUTING Eric Lagatta, Paste BN
SOURCE Paste BN Network reporting and research; Reuters; NASA; University of Cambridge; earth.com; The Astrophysical Journal Letters; space.com; Nature; European Space Agency