Scientists have developed a new method to detect ancient microbial life in Martian gypsum, potentially guiding future Mars exploration missions. A team led by Youcef Sellam, a Ph.D. student at the Physics Institute of the University of Bern, demonstrated that their instrument can detect signatures of life in gypsum. "Our findings provide a methodological framework for detecting biosignatures in Martian sulfate minerals, potentially guiding future Mars exploration missions," said Sellam.
In their study, the scientists identified long, twisting fossil filaments within gypsum samples from Algeria. Sellam stated that these were ancient, fossilized microbes, indicating that gypsum could preserve life. "We proved that our instrument is capable of detecting signatures of life in gypsum," he added, suggesting it might help do the same on Mars.
The research focused on gypsum formations that developed during the Messinian Salinity Crisis, a period when the Mediterranean Sea was cut off from the Atlantic Ocean. "The Messinian Salinity Crisis occurred when the Mediterranean Sea was cut off from the Atlantic Ocean. This led to rapid evaporation, causing the sea to become hypersaline and depositing thick layers of evaporites, including gypsum. These deposits provide an excellent terrestrial analog for Martian sulfate deposits," explained Sellam.
The scientists sampled gypsum from the Sidi Boutbal quarry in Algeria. They selected a miniature laser-powered mass spectrometer that could be used on a spaceflight. This instrument can analyze the chemical composition of a sample in detail as fine as a micrometer. They analyzed the gypsum using the mass spectrometer and an optical microscope.
The analysis was guided by criteria to distinguish between potential microbial fossils and natural rock formations. These criteria include irregular, sinuous, and potentially hollow morphology. The filaments observed have previously been interpreted as benthic algae or cyanobacteria. They are now thought to be sulfur-oxidizing bacteria like Beggiatoa. The filaments were embedded in gypsum and surrounded by dolomite, clay minerals, and pyrite. The presence of dolomite, clay minerals, and pyrite signals the presence of organic life.
Prokaryotes facilitate dolomite formation in an acidic environment like Mars by increasing alkalinity and concentrating ions in their cell envelopes. For dolomite to form within gypsum without the presence of organic life, high temperatures and pressures would be needed that would have dehydrated the gypsum. These conditions are not consistent with our knowledge of the Martian environment. If mass spectrometers identify the presence of clay and dolomite in Martian gypsum in addition to other biosignatures, this could be a key signal of fossilized life.
"While our findings strongly support the biogenicity of the fossil filament in gypsum, distinguishing true biosignatures from abiotic mineral formations remains a challenge," cautioned Sellam, according to Phys.org. He added, "An additional independent detection method would improve the confidence in life detection. Additionally, Mars has unique environmental conditions which could affect biosignature preservation over geological periods. Further studies are needed."
Sellam expressed pride in his contributions. "As an Algerian researcher, I am incredibly proud to have introduced my country to the field of planetary science," he said, as reported by Phys.org. He is also proud that his first scientific publication highlights Algeria, his home country. "This research is the first astrobiology study to involve Algeria and the first to use an Algerian terrestrial analog for Mars," he added.
Sellam's journey began years earlier. According to NPR, he and his father traveled north to a gypsum quarry near the Mediterranean coast of Algeria. "I was the one making the sampling while my dad was just watching!" Sellam recalled. Over a couple of days, he collected more than 60 pounds of gypsum using a hammer and chisel.
After returning to the lab, Sellam discovered sinuous filaments preserved in the gypsum samples. "Because they are fossils, we cannot be 100% sure about the species. They might have been a kind of algae or bacteria," he said. His Ph.D. focused on testing whether a laser ablation ionization mass spectrometer (LIMS) could detect chemical traces of ancient microbes in gypsum. "It's basically a laser beam hitting the sample. And this laser will vaporize part of the material, creating some atoms. You will have a spectra of the different elements that are existing in the rock," he explained.
Looking at those spectra can determine whether there's fossilized life in the rock. Sellam used his Algerian gypsum samples to test the laser instrument on Earth. Bonnie Baxter, a biochemist at Westminster University, commented on the significance of the study. "What this study in Algeria really does is it highlights that you can use chemical methods to infer that biology is in the mineral," she said, according to NPR. "And chemical methods are just a little more transferable to Mars."
The article was written with the assistance of a news analysis system.