Scientists have developed a laser-based device that could be installed on a future Mars rover as a tool for finding signs of former life on the Red Planet.

The University of Bern team has developed a miniature, laser-powered mass spectrometer that can analyse the chemical composition of a rock sample in detail as fine as a micrometre (one-thousandth of a millimetre). 

The tool has already been used to sample gypsum from a quarry in Algeria in an attempt to replicate the kind of materials and conditions that might be experienced on Mars. The team analysed the rock using the tool to understand its ability to 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 such as clay or dolomite, which can be influenced by the presence of bacteria.

“Gypsum has been widely detected on the Martian surface and is known for its exceptional fossilisation potential,” said Youcef Sellam, PhD student and first author on the study. “It forms rapidly, trapping microorganisms before decomposition occurs, and preserves biological structures and chemical biosignatures.”

Gypsum and other sulphates formed on Mars after its liquid water evaporated due to atmospheric changes. This left behind minerals that precipitated out of the water and potentially fossilised any organic life left behind. This means that if microbes such as bacteria lived there, traces of their presence could be preserved as fossils. 

The scientists identified long, twisting fossil filaments within the Algerian gypsum, which are thought to be sulphur-oxidising bacteria such as Beggiatoa. These were embedded in gypsum, and surrounded by dolomite, clay minerals and pyrite. 

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 – this would not be consistent with our knowledge of the Martian environment. 

If the mass spectrometer is able to identify the presence of clay and dolomite in Martian gypsum, this could be a key signal of fossilised life, which could be reinforced by analysing other chemical minerals present and by looking for similar organically formed filaments. 

“Our findings provide a methodological framework for detecting biosignatures in Martian sulphate minerals, potentially guiding future Mars exploration missions,” Sellam explained. “Our laser ablation ionisation mass spectrometer, a spaceflight-prototype instrument, can effectively detect biosignatures in sulphate minerals. This technology could be integrated into future Mars rovers or landers for in-situ analysis.”

Last year, Nasa’s Perseverance rover analysed a rock on Mars that had “some indications” it may have hosted microbial life billions of years ago. But the tools onboard the rover are not advanced enough to definitively determine whether it is life or not at this stage.

Nasa was recently forced to delay work on its Mars Sample Return plan while it assesses two possible approaches on how to successfully fulfil the tricky mission.