Space & Cosmos

Indicators of possible life on other planets can be created in the lab

Diagram of the general methodology. “Sorg” stands for “organic sulfur gases,” “GC” for “gas chromatography,” and “SCD” for “sulfur chemiluminescence detection.” Credit: The Astrophysical Journal Letters (2024). DOI: 10.3847/2041-8213/ad74da

One way to understand the possibility of life on distant planets — planets in other solar systems orbiting other stars — is to study their atmospheres. Images taken with telescopes often show traces of gas that could indicate the presence of life or a habitable planet. But new findings led by researchers at the University of Colorado Boulder call this idea into question. Scientists have created a type of gas often seen as an indicator of life in a lifeless chemistry lab.

A paper published today in the Astrophysical Journal Letters suggests that biosignatures, a type of molecule that scientists typically consider a sign of life, may not be as powerful an indicator of life as previously thought. Using gases and light present in the atmospheres of many planets, the researchers produced dimethyl sulfide (a type of organosulfur compound often produced by marine microbes) in a reaction chamber.

The researchers said that while producing dimethyl sulfide in the lab was exciting, their findings overturn previous work. The study was led by Nate Reed, visiting scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder, and Ellie Brown, a CIRES research scientist and associate professor of chemistry.

“The sulfur molecules we’re making are thought to be indicators of life because they are produced by life on Earth,” Brown said. “But we made them in the lab in lifeless conditions, so while they may not be a sign of life, they could be a sign of an environment that could support life.” According to the study authors, organosulfur compounds may not be strong biomarkers, but they could serve as markers of metabolic capacity.

In Search of Life

NASA’s James Webb Space Telescope was launched in 2009. One of its missions is to take images of exoplanets (planets outside Earth’s solar system) and understand their different atmospheres. Part of the satellite’s mission is to ask the question of whether life exists on these planets.

The new study examines what happens in the planet’s atmosphere when gases react with light to form “organic haze and associated gases,” aerosol particles that form through atmospheric chemical reactions. The authors focused on sulfur-containing organic molecules such as dimethyl sulfide, a secondary metabolite of organisms on Earth.

“One of the big findings in the paper that we looked at was dimethyl sulfide,” Reid said, “which was a really exciting discovery because it’s been measured in the atmospheres of exoplanets and has previously been thought to be evidence that planets could be habitable.”

To recreate the planet’s atmosphere in the lab, Reed and Brown, along with their co-authors, including CIRES Associate Director Maggie Tolbert, mimicked an atmosphere in which light reacts with gases. In the new study, they used ultraviolet light to turn methane and hydrogen sulfide molecules into reactive species, producing organosulfur gases, the biosignatures observed by the James Webb Space Telescope.

Reid noted that while the findings are intriguing, they are limited to a specific type of atmosphere: “There are many different types of atmospheres, and we only looked at a small variation in one of them. You can’t study all the atmospheres that exist in a lab,” he said.

The researchers hope that this work will inspire more fundamental laboratory studies looking at basic chemical reactions, particularly involving sulfur, which is sticky, smelly, and toxic, making it difficult to work with. But without studying sulfur’s reactions, scientists won’t be able to fully understand what these findings mean about biosignatures.

“When we’re looking for these signs of life, we tend to want to sensationalize it and say, ‘We’ve found signs of life,'” Brown said. “It turns out that the atmosphere is well suited to producing a whole range of molecules, and just because we can make them in the lab doesn’t mean they can’t be a source of life.”

Further information: Nathan W. Reed et al., “Abiotic production of dimethyl sulfide, carbonyl sulfide, and other organosulfur gases by photochemistry: Implications for biosignatures and metabolic potential.” The Astrophysical Journal Letters (2024). DOI: 10.3847/2041-8213/ad74da

Courtesy of University of Colorado Boulder

Source: Lab could create potential indicators of possible life on other planets (September 23, 2024) Retrieved September 23, 2024 from https://phys.org/news/2024-09-potential-indicators-life-planets-lab.html

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