For a long time now scientists have been trying to find life on Mars, but so far have come up empty-handed. Even if they did discover something, it’s unlikely to be the little green men we’re all used to seeing in the movies. Instead, it would probably be in the form of fossilized bacteria. And, this isn’t something we’re likely to just see. Machines like the Mars rover would be needed in order to perform a proper detailed analysis of the planet’s rock samples to see what can be uncovered.
A new study carried out suggests that if we want to find proof of alien life on Mars we should first look for the chemical element vanadium. “You’ve got your work cut out if you’re looking at the ancient sedimentary rock for microfossils here on Earth – and even more so on Mars,” said the paper’s lead author and an associate professor at the University of Kansas, Craig Marshall. “On Earth, the rocks have been here for 3.5 billion years, and tectonic collisions and realignments have put a lot of stress and pressure on the rocks. Also, these rocks can get buried, and temperature increases with depth.”
One technique that’s been used quite a lot when it comes to hunting for life on Mars is the Raman spectroscopy. This technique can reveal a sample’s cellular composition and is an important piece of equipment. “People say, ‘If it looks like life and has a Raman signal of carbon, then we have life,” says Marshall. “But, of course, we know there can be carbonaceous materials made in other processes – like hydrothermal vents – consistent with looking like microfossils that also have some carbon signal. People also make wonderful carbon structures artificially that look like microfossils – exactly the same. So, we’re at a juncture now where it’s really hard to tell if there’s life only based on morphology and Raman spectroscopy.”
In Marshall and team’s paper, they demonstrate how they believe microfossils were once alive. The technique they used could also be used in the planned NASA 2020 rover mission to see if life really is up there. “We applied a new technique called X-ray fluorescence microscopy – it looks at elemental composition,” confirmed Marshall. “Vanadium is an element in the periodic table, a transition metal. It’s been shown it can substitute into biological compounds. If you can’t unambiguously assign is something is biology or not with morphology and Raman spectroscopy in tandem – maybe we could look for a known biological element, like vanadium. Then, if the material that looked like a microfossil, and looked carbonaceous with Raman spectroscopy – and had vanadium – that’s a new way forward for finding out if something really was biology.”
Usually, magnesium is found to be at the center of chlorophyll, but, “under burial, vanadium replaces the magnesium”, explains Marshall. “The chlorophyll molecule gets entangled within the carbonaceous material, thus preserving the vanadium.” To prove the concept of testing vanadium on known microfossils Marshall and colleagues used acritarchs. “We tested acritarchs to do a proof-of-concept on a microfossil where there’s no shadow of a doubt that we’re looking at preserved ancient biology,” Marshall commented.
Peter Lay is a researcher at the University of Sydney and is the co-author of the study. “We plan to undertake further Raman spectroscopic work on the carbonaceous materials using nanospectroscopic imaging,” he said. “This research is also of interest to researchers in the European space program on the Mars Explorer, since another investigator on the ARC grant, although not working on this aspect, was Howell Edwards, who was involved in instrumentation for the Mars Explorer.
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