On a distant exoplanet, Astronomers detect strongest signal of life ever recorded

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The search for life beyond Earth has led scientists to explore many suggestive mysteries, from plumes of methane on Mars to clouds of phosphine gas on Venus. But as far as we can tell, Earth’s inhabitants remain alone in the cosmos.

Now a team of researchers is offering what it contends is the strongest indication yet of extraterrestrial life, not in our solar system but on a massive planet, known as K2-18b, that orbits a star 120 light-years from Earth. A repeated analysis of the exoplanet’s atmosphere suggests an abundance of a molecule that on Earth has only one known source: living organisms such as marine algae.

“It is in no one’s interest to claim prematurely that we have detected life,” said Nikku Madhusudhan, an astronomer at the University of Cambridge and an author of the new study, at a news conference on Tuesday. Still, he said, the best explanation for his group’s observations is that K2-18b is covered with a warm ocean, brimming with life.

“This is a revolutionary moment,” Dr. Madhusudhan said. “It’s the first time humanity has seen potential biosignatures on a habitable planet.”

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While inspecting K2-18b, Dr. Madhusudhan and his colleagues discovered it had many of the molecules they had predicted a Hycean planet would possess. In 2023, they reported they had also detected faint hints of another molecule, and one of huge potential importance: dimethyl sulfide, which is made of sulfur, carbon, and hydrogen.

On Earth, the only known source of dimethyl sulfide is life. In the ocean, for instance, certain forms of algae produce the compound, which wafts into the air and adds to the sea’s distinctive odor. Long before the Webb telescope was launched, astrobiologists had wondered whether dimethyl sulfide might serve as a sign of life on other planets.

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Last year, Dr. Madhusudhan and his colleagues got a second chance to look for dimethyl sulfide. As K2-18b orbited in front of its star, they used a different instrument on the Webb telescope to analyze the starlight passing through the planet’s atmosphere. This time they saw an even stronger signal of dimethyl sulfide, along with a similar molecule called dimethyl disulfide.

“It is a shock to the system,” Dr. Madhusudhan said. “We spent an enormous amount of time just trying to get rid of the signal.”

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No matter how the scientists revisited their readings, the signal stayed strong. They concluded that K2-18b may in fact harbor a tremendous supply of dimethyl sulfide in its atmosphere, thousands of times higher than the level found on Earth. This would suggest that its Hycean seas are brimming with life.

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Neat stuff!!

I asked my friend who is an astronomy professor at uc-Irvine about this and he said it has had the astronomy world buzzing for a few weeks now when it started making the rounds in astronomy circles. Basically he told me it’s the most significant finding re: cellular life on other planets since research began. He said there is one reason astronomers cannot stop talking about this story: the presence of dimethyl sulfide on this exoplanet