Is our beautiful planet but one of billions of living planets in the cosmos? How would discovering life elsewhere in the Universe change our perspective on God, existence, and everything we think we know to be true? I’m not necessarily talking about advanced life forms, merely the real possibility that life in the cosmos is much more abundant than we believe. Our planet is special, but could it be one of countless ‘special’ planets? I sure hope so. 

– 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.”

The study was published Wednesday in the Astrophysical Journal Letters. Other researchers called it an exciting, thought-provoking first step to making sense of what’s on K2-18b. 

Canadian astronomers discovered K2-18b in 2017, while looking through ground-based telescopes in Chile. It was a type of planet commonly found outside our solar system, but one without any analog near Earth that scientists could study closely for clues.

These planets, known as sub-Neptunes, are much bigger than the rocky planets in our inner solar system, but smaller than Neptune and other gas-dominated planets of the outer solar system.

In 2021, Dr. Madhusudhan and his colleagues proposed that sub-Neptunes were covered with warm oceans of water and wrapped in atmospheres containing hydrogen, methane and other carbon compounds. To describe these strange planets, they coined a new term, “Hycean,” from a combination of the words “hydrogen” and “ocean.”

The launch of the James Webb Space Telescope in December 2021 allowed astronomers a closer look at sub-Neptunes and other distant planets.

As an exoplanet passes in front its host star, its atmosphere, if it has one, is illuminated. Its gases change the color of the starlight that reaches the Webb telescope. By analyzing these changing wavelengths, scientists can infer the chemical composition of the atmosphere.

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.

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.”

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.

“It’s important to remember that we’re just starting to understand the nature of these exotic worlds,” said Matthew Nixon, a planetary scientist at the University of Maryland who was not involved in the new study.

Researchers want to wait to see what the Webb telescope finds as it continues to examine K2-18b; provocative early findings sometimes fade in the light of additional data. 

NASA has been designing and building more powerful space telescopes that will look specifically for signs of habitability on planets orbiting other stars, including K2-18b. Even if it takes years to decipher what’s happening on K2-18b, it could be worth it, scientists said.

“I’m not screaming, ‘aliens!’” said Nikole Lewis, an exoplanetary scientist at Cornell University. “But I always reserve my right to scream ‘aliens!’”

But Joshua Krissansen-Totton, an astrobiologist at the University of Washington, said he worried that American astrobiologists may not be able to follow up on the latest results on K2-18b.

The Trump administration is reportedly planning to cut NASA’s science budget in half, eliminating future space telescope and other astrobiology projects. If that happens, Dr. Krissansen-Totton said, “the search for life elsewhere would basically stop.”

By Carl Zimmer – New York Times – April 16, 2025.

MILLIONS OF PLANETS: Scientists have stunned the world with the news that life likely does exist on a faraway planet. 

K2-18b – which is more than twice as big as Earth and 120 light-years away – sits within the habitable zone of its star in the Leo constellation.

According to a new University of Cambridge study, its atmosphere contains huge quantities of chemicals, which on Earth are only made by living organisms. 

Planet K2-18b is a suspected a ‘hycean’ world – a rocky planet with a hydrogen-rich atmosphere and vast oceans of water.

It’s probable that K2-18b’s oceans are filled with something like phytoplankton – tiny organisms that feed on the energy from the nearby star.

But what’s exciting is that K2-18b is very unlikely to be a one-off in the universe – meaning many others that are similar likely exist too. 

Peter Vickers, a philosophy of science professor at Durham University, said there are likely ‘millions’ of planets outside our galaxy hosting some kind of lifeforms. 

‘If it does turn out that K2-18b has life, then it is virtually guaranteed that there are million more exoplanets harbouring extraterrestrial life,’ he told MailOnline.

Apr 17, 2025 4:32:53 pm