Scientists find ‘strongest evidence’ yet for life beyond Earth

New molecules discovered on a faraway exoplanet have given scientists the "strongest evidence yet" that life may exist beyond Earth. 

A Cambridge University team using NASA’s James Webb Space Telescope to study the K2-18b exoplanet has found signs of molecules that – on Earth – can only be made by simple organisms. They caution that it’s far too soon to make any conclusions about life on the exoplanet – much more data is needed to understand what’s happening on K2-18b. 

What did scientists find on K2-18b?

Big picture view:

While studying K2-18b, the Cambridge team detected the chemical fingerprints of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS). The team says that on Earth, DMS and DMDS are only produced by life, "primarily microbial life such as marine phytoplankton."

RELATED: Astronomers find 'Tatooine' planet orbiting two stars

The latest findings provide more evidence that K2-18b may be covered with a warm ocean that’s conducive to life. 

Dig deeper:

Scientists noted that the concentrations of DMS and DMDS in K2-18b’s atmosphere are very different from here on Earth, where they are generally below 1 part per billion by volume. On K2-18b, they are estimated to be thousands of times stronger - over 10 parts per million.

What they're saying:

"It is in no one’s interest to claim prematurely that we have detected life," Dr. Nikku Madhusudhan, an astronomer at the University of Cambridge and an author of the new study, said during a news conference Tuesday. 

RELATED: Astronomers say new 'star' due to appear in night sky is 'late to the party'

"It’s important that we’re deeply sceptical of our own results, because it’s only by testing and testing again that we will be able to reach the point where we’re confident in them," Madhusudhan said. "That’s how science has to work."

Still, he called it "a revolutionary moment."

"It’s the first time humanity has seen potential biosignatures on a habitable planet," Madhusudhan said. 

"This is the strongest evidence yet there is possibly life out there. I can realistically say that we can confirm this signal within one to two years," he told BBC. 

What's next:

Madhusudhan wants to conduct further theoretical and experimental work to determine whether DMS and DMDS can be produced non-biologically at the level currently detected.

What is K2-18b? 

The backstory:

Discovered in 2015, the planet known as K2-18b is 2.6 times the size of Earth with eight times the mass. While it’s thought to be rocky, no one knows if water’s flowing on the surface. Its star, a red dwarf, is considerably smaller and cooler than our sun, a yellow dwarf, and its atmosphere is also different than ours.

It’s 124 light-years away from Earth in the constellation Leo, and it’s just the right distance from its star to conceivably harbor life. 

RELATED: New comet spotted: How to see SWAN25F

In 2019, scientists announced that they found water vapor in K2-18b’s atmosphere – a tantalizing first at the time. Those findings were consistent with the potential for a "Hycean" planet: "a habitable ocean-covered world underneath a hydrogen-rich atmosphere," according to the University of Cambridge. 

It’s the only exoplanet known so far to have both water and temperatures needed for life, the University College London team reported in the journal Nature Astronomy in 2019. But lead author Angelos Tsiaras stressed, "This is definitely not a second Earth."

Its star and atmosphere are so different than ours, "Earth-like conditions are not possible," Tsiaras said. "The only question that we’re trying to ask here, and we’re pushing forward, is the question of habitability."

The James Webb Space Telescope launched in December 2021 as the world’s biggest and most powerful telescope. It offers the deepest look of the cosmos ever captured, closer to the dawn of time and the edge of the universe.