Scientists may finally have a way to detect ancient life on Mars by studying microbial fossils preserved in sulfate minerals.

Gypsum deposits on Mars may be hiding evidence of past microbial life — similar to the first organisms that appeared on Earth four billion years ago. But proving this theory requires the right tools. Scientists have now tested a miniature, laser-powered mass spectrometer designed for space missions. This instrument successfully identified microbial fossils in Earth’s gypsum deposits, which formed under conditions similar to sulfate deposits on Mars. The researchers hope this technology will soon be used on Mars to search for signs of ancient life.

Ancient Life on Mars? A New Way to Find Out

The first life on Earth emerged around four billion years ago, taking the form of microbes thriving in ancient pools and seas. But what if something similar happened on Mars? And if it did, how could we prove it?

Researchers searching for fossil evidence of ancient Martian microbes have taken a significant step forward. They have demonstrated that microbial fossils can be detected in gypsum samples — minerals that closely resemble sulfate rocks found on Mars. This breakthrough suggests that similar techniques could be used to identify traces of past life on the Red Planet.

“Our findings provide a methodological framework for detecting biosignatures in Martian sulfate minerals, potentially guiding future Mars exploration missions,” said Youcef Sellam, PhD student at the Physics Institute, University of Bern, and first author of the article in Frontiers in Astronomy and Space Sciences. “Our laser ablation ionization mass spectrometer, a spaceflight-prototype instrument, can effectively detect biosignatures in sulfate minerals. This technology could be integrated into future Mars rovers or landers for in-situ analysis.”

Water, Minerals, and the Possibility of Fossils

Billions of years ago, Mars was covered in water, but as it dried up, minerals like gypsum and other sulfates formed from evaporating pools. These minerals could have preserved any microbial life that once existed, fossilizing traces of ancient bacteria within their structures. If microbial life ever flourished in Mars’ watery past, its remains may still be locked inside these minerals, waiting to be discovered.

“Gypsum has been widely detected on the Martian surface and is known for its exceptional fossilization potential,” explained Sellam. “It forms rapidly, trapping microorganisms before decomposition occurs, and preserves biological structures and chemical biosignatures.”

But to identify these microbial fossils we first need to prove we can identify similar fossils in places where we know such microbes existed — such as Mediterranean gypsum formations that developed during the Messinian Salinity Crisis.

“The Messinian Salinity Crisis occurred when the Mediterranean Sea was cut off from the Atlantic Ocean,” said Sellam. “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.”

The scientists selected an instrument that could be used on a spaceflight: a miniature laser-powered mass spectrometer, which can analyze the chemical composition of a sample in detail as fine as a micrometer. They sampled gypsum from Sidi Boutbal quarry, Algeria, and analyzed it using the mass spectrometer and an optical microscope, guided by criteria which can help distinguish between potential microbial fossils and natural rock formations.

These include morphology, which is irregular, sinuous, and potentially hollow, as well as the presence of chemical elements necessary for life, carbonaceous material, and minerals like clay or dolomite, which can be influenced by the presence of bacteria.

Did Life Once Thrive on Mars?

The scientists identified long, twisting fossil filaments within the Algerian gypsum, which have previously been interpreted as benthic algae or cyanobacteria, and are now thought to be sulfur-oxidizing bacteria like Beggiatoa. These were embedded in gypsum, and surrounded by dolomite, clay minerals, and pyrite.

The presence of these minerals signals the presence of organic life, because prokaryotes — cells without a nucleus — supply elements which clay needs to form. They also facilitate dolomite formation in an acidic environment like Mars by increasing the alkalinity around them 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, and which aren’t consistent with our knowledge of the Martian environment.

Could We Finally Detect Life on the Red Planet?

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, which could be reinforced by analyzing other chemical minerals present and by looking for similar organically formed filaments.

“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. “An additional independent detection method would improve the Perseverance confidence in life detection. Additionally, Mars has unique environmental conditions, which could affect biosignature preservation over geological periods. Further studies are needed.”

A Personal and Scientific Milestone

“This research is the first astrobiology study to involve Algeria and the first to use an Algerian terrestrial analog for 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 of my life. I hope that he is proud of what I have achieved.”

Reference: “The search for ancient life on Mars using morphological and mass spectrometric analysis: an analog study in detecting microfossils in Messinian gypsum” by Youcef Sellam, Salome Gruchola, Marek Tulej, Peter Keresztes Schmidt, Andreas Riedo, Sofiane Meddane and Peter Wurz, 8 January 2025, Frontiers in Astronomy and Space Sciences.
DOI: 10.3389/fspas.2025.1503042