Is Dimethyl Sulfide Actually a Signal of Alien Life?

Is Dimethyl Sulfide Actually a Signal of Alien Life?

By Meghan Bartels edited by Dean Visser

Scientists and extraterrestrial fanatics are abuzz after a group of researchers learning the ambiance of an exoplanet referred to as K2-18 b with NASA’s James Webb House Telescope (JWST) simply introduced that they detected excessive ranges of both the chemical dimethyl sulfide or a really related compound—billing it as a touch of alien life. Though most individuals have by no means heard of dimethyl sulfide, it’s throughout us right here on Earth. However what is that this compound, and is it actually an indication of life past Earth?

What Is Dimethyl Sulfide?

In chemical phrases, dimethyl sulfide includes one atom of sulfur bonded to 2 methyl teams, every of which incorporates one carbon atom and three hydrogen atoms. The result’s a small molecule with an outsize potential to offend the human nostril. “Any of those sulfur issues are going to be tremendous pungent—that garlic, rotten egg scent,” says Eleanor Browne, a chemist on the College of Colorado Boulder.

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Earth’s dimethyl sulfide is consistently being produced by tiny plankton within the oceans. From there, it rises into the ambiance, the place it makes up about one out of each billion molecules. As soon as aloft, every particular person molecule of dimethyl sulfide lasts solely hours or, at most, a couple of day earlier than it’s destroyed in reactions which can be triggered by publicity to daylight and numerous atmospheric compounds.

That course of is scientifically vital right here on the floor, Browne says, as a result of these reactions finally create tiny particles referred to as aerosols that seed clouds, making dimethyl sulfide an vital compound to know for local weather fashions and different atmospheric science.

From Earth to K2-18 b

As a result of microbes produce all the detectable dimethyl sulfide in Earth’s ambiance, and since it breaks down so shortly, scientists have lengthy held that the compound might be a so-called biosignature—a fingerprint of life that’s detectable from a distance—on different planets removed from our personal. “On Earth, it’s thought-about actually a clear, unambiguous biosignature,” says Nora Hänni, a chemist on the College of Bern in Switzerland.

Enter JWST, a chunk of know-how with an unprecedented potential to smell out atmospheric chemical compounds on planets that move between their stars and the telescope. Scientists organized for JWST to check K2-18 b, which had been found orbiting a small, cool star about 124 light-years from Earth in 2015. The exoplanet’s measurement seems to be between that of Earth and Neptune and belongs to a spread that scientists have by no means seen up shut.

In 2023 researchers led by Nikku Madhusudhan, an astrophysicist on the College of Cambridge, introduced the primary indicators of dimethyl sulfide in K2-18 b’s ambiance. At the moment, different scientists had been unable to corroborate the detection. However on Wednesday Madhusudhan and his group introduced {that a} second JWST instrument had detected both the compound or the same potential biosignature, dimethyl disulfide, with extra confidence than the earlier observations and at a lot increased ranges than these in Earth’s ambiance. The brand new outcomes had been printed on April 17 within the Astrophysical Journal Letters.

“You want 1000’s of occasions of Earth’s concentrations to have the ability to clarify the information,” he mentioned throughout a presentation broadcast on YouTube on April 17.

Taking the “Bio” Out of Biosignature?

From the brand new JWST observations—and the calculation that K2-18 b lies at a distance from its star that might allow liquid water to stay on its floor—Madhusudhan concluded that probably the most logical clarification is that the planet is roofed in an ocean of heat water that’s “teeming with life,” he mentioned through the presentation on Thursday.

However each Hänni and Browne performed latest analysis that confirmed it will be a stretch to depend on dimethyl sulfide as a conclusive signal of life. Browne and her colleagues produced it and related compounds in a laboratory simulation of Earth’s early ambiance—with out together with dwelling organisms. Hänni and her group detected the molecule on a frozen comet referred to as 67P/Churyumov-Gerasimenko, which the European House Company explored up shut with its Rosetta mission.

Each researchers emphasize that scientists don’t know practically sufficient about K2-18 b to find out whether or not any dimethyl sulfide present in its ambiance was produced by dwelling organisms—or by abiotic happenstance of the type that led to their very own observations. Researchers don’t even know whether or not the compound would disappear as quickly because it does in Earth’s nitrogen-rich ambiance, provided that the alien world’s ambiance is dominated by carbon dioxide as an alternative.

“Chemistry and the planets and all of these processes are so various,” Browne says. “There’s all the time going to be a method to make one thing abiotically.”

And if life is producing the dimethyl sulfide, that very same life needs to be producing different compounds as properly, says Chris Lintott, an astronomer on the College of Oxford. “[Dimethyl sulfide] ought to exist in a chemical community. If it’s produced by biology, it ought to break down, and the uncooked supplies—akin to H₂S [hydrogen sulfide]—used to make it needs to be seen within the spectrum, too. They aren’t.”

Total, he argues that native context will all the time decide what makes one thing a biosignature. “In search of what’s organic on Earth isn’t information to what is perhaps organic elsewhere,” he says.