Laser-Powered Technique Offers New Method to Find Fossilised Microbes on Mars

Scientists test a laser-powered mass spectrometer on gypsum samples, demonstrating a possible approach for potentially detecting ancient life on Mars.

• Miniature mass spectrometer demonstrates micrometre-scale analysis of microbial fossils in gypsum
• Gypsum chosen for its suitability as a terrestrial analogue to Martian sulfates
• Potential for integration of the technique into future Mars rover or lander instruments

Researchers have shown that a compact, laser-powered mass spectrometer can identify microscopic fossils in terrestrial gypsum, a mineral known to exist on the Martian surface. Although these tests were conducted on Earth, the method they employed could, in theory, be adapted for future Mars missions, potentially offering a new tool for detecting traces of ancient life on the Red Planet.

Verifying Microbial Fossils in Gypsum

“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.”

In this study, the team examined gypsum samples from Sidi Boutbal quarry in Algeria, chosen for its close resemblance to conditions once present on Mars. Gypsum is formed when water evaporates and leaves behind sulphate minerals. If microbes, such as bacteria, had been present in the evaporating water, they could be fossilised within the mineral. Testing the ability to detect such fossils on Earth is an essential step before applying the same technique to Martian geology.

“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.”

The researchers analysed the gypsum to identify distinctive features that suggest past microbial activity. They looked for morphological structures like sinuous filaments, as well as chemical evidence such as carbonaceous material, dolomite, clay and pyrite. These minerals can result from biological processes, though determining whether they are truly biogenic often requires multiple lines of evidence.

Potential Application in Mars Missions

Central to this approach is the laser ablation ionisation mass spectrometer, which uses a finely focused laser to vaporise tiny parts of a sample, converting them into ions. These ions are then examined based on their mass-to-charge ratio, painting a detailed picture of the sample’s chemical composition at a micrometre scale. When combined with microscopic imaging, the technique can pinpoint exactly where organic and mineral signals overlap, improving confidence in identifying potential biosignatures.

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

By studying these earthly samples and confirming the detection of long, twisting fossil filaments and associated minerals, researchers gained insights into how future Mars missions might proceed. If, for instance, a rover equipped with a similar mass spectrometer were to find both clay and dolomite in Martian gypsum, it would be a strong clue that ancient microbial life might have been preserved within the rock record. However, as Sellam noted, caution is necessary: “While our findings strongly support the biogenicity of the fossil filament in gypsum, distinguishing true biosignatures from abiotic mineral formations remains a challenge. An additional independent detection method would improve the confidence in life detection.”

Moreover, potential preservation issues on Mars could complicate analysis. Over billions of years, the Red Planet’s surface has been subjected to extreme conditions, including cosmic radiation, temperature fluctuations and a thin atmosphere. Future investigations may need to factor in these differences to interpret findings accurately.

“This research is the first astrobiology study to involve Algeria and the first to use an Algerian terrestrial analog for Mars,” said Sellam, who also dedicated the work to his late father. These personal and national milestones underline the global importance of exploring planetary science from multiple angles. As the quest to uncover evidence of past life on Mars continues, refining techniques such as laser ablation ionisation mass spectrometry will remain central to astrobiology’s next steps.