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Mars has captivated scientists for years in their search for signs of life beyond Earth. Although its dry, dusty terrain seems inhospitable today, the Red Planet once had water billions of years ago. Basins and seas may have once covered the surface, much like early Earth. If life had originated there, as it does here, could there be traces of ancient Martian microbes?
A team of researchers believe they may have found a way to answer that question. By studying gypsum, a mineral known for preserving fossils, they have shown that microbial life can leave biosignatures in sulfate minerals. The findings could shape future exploration of Mars, helping scientists determine whether life once flourished on the barren planet.
Discovery of ancient life on Mars
Detecting evidence of ancient life on another planet is a difficult task. Any method must be reliable, precise and able to work in Martian conditions. Researchers from the University of Bern have taken a significant step forward by testing a laser-powered mass spectrometer on terrestrial gypsum samples. This instrument, developed for space missions, can identify biosignatures at the microscopic level. The study's first author, Youssef Sellam, is a doctoral student at the Institute of Physics at the University of Bern.
"Our findings provide a methodological framework for detecting biosignatures in Martian sulfate minerals, potentially guiding future Mars exploration missions," Sellam said.
"Our laser ablation ionization mass spectrometer, a prototype spaceflight instrument, can effectively detect biosignatures in sulfate minerals. This technology could be integrated into future Mars rovers or landers for in-situ analysis."
Searching for microbes
Mars once had plenty of water, but over time it dried up. Gypsum and other sulfates formed when these bodies of water evaporated, potentially preserving organic life on Mars. If microbes existed, their fossils could still be present in these minerals.
"Gypsum has been widely discovered on the surface of Mars and is known for its exceptional fossilization potential," Sellam explained. "It forms rapidly, trapping microorganisms before decomposition begins, and preserves biological structures and chemical biosignatures."
To test this, the scientists tested their detection methods on terrestrial gypsum, where microbial fossils are known to exist. They examined Mediterranean gypsum formations created during the Messinian salinity crisis.
"The Messinian salinity crisis occurred when the Mediterranean Sea was cut off from the Atlantic Ocean," Sellam said.
"This led to rapid evaporation, causing the sea to become hypersaline and depositing thick layers of evaporites, including gypsum. These deposits are a remarkable terrestrial analogue of Martian sulfate deposits."
In search of vital elements
The scientists needed an instrument that could function in a space mission. They chose a compact laser mass spectrometer, which can analyze chemical composition at a microscopic level. They collected gypsum from the Sidi Boutabal quarry in Algeria and examined it using a mass spectrometer and an optical microscope. Specific characteristics helped distinguish microbial fossils from natural rock formations. These included irregular shapes, the presence of vital elements, carbon-based material, and minerals such as clay or dolomite that are affected by bacterial activity.
Signs of life on Mars
Researchers have discovered long, winding fossil filaments in Algerian gypsum. Previously thought to be benthic algae or cyanobacteria, these structures are now thought to be sulfur-oxidizing bacteria, like Beggiatoa These bacteria were embedded in gypsum and surrounded by dolomite, clay minerals, and pyrite.
The presence of these minerals indicates biological activity. Prokaryotic cells influence the formation of clay by supplying necessary elements. They also contribute to the formation of dolomite in acidic environments such as Mars, increasing alkalinity and concentrating ions in their environment.
Without organic life, dolomite would require extreme heat and pressure to form into gypsum, conditions that are unlikely to exist on Mars. If Martian gypsum contains clay, dolomite, and other biosignatures, it could indicate fossilized life. Scientists can confirm this by analyzing additional minerals and looking for similar organic structures.
Further research is needed
"While our findings strongly support the biogenicity of fossil filaments in gypsum, distinguishing true biosignatures from abiotic mineral formations remains a challenge," Sellam said. He noted that an additional independent detection method would increase confidence in the detection of life.
"In addition, Mars has unique environmental conditions that may affect the preservation of biosignatures over geological timescales. Further research is needed."
The role of Algeria in planetology
“This study is the first astrobiological study involving Algeria and the first to use an Algerian terrestrial analogue of Mars,” said Sellam. “As an Algerian researcher, I am incredibly proud to have introduced my country to the field of planetary science.
"This work is also dedicated to the memory of my father, who was a great source of strength and encouragement. Losing him during this research was one of the most difficult moments in my life. I hope he is proud of what I have achieved." The study is published in the journal Frontiers in Astronomy and Space Sciences.
