Finding signs of life on Mars is one of the main reasons to send probes to the planet. But it is possible that the instruments sent to Mars so far are not sensitive enough for this. Because their technology is not even enough to find life on Earth. A team led by Armando Azua-Bustos of the Centro de Astrobiología in Madrid came to this surprising result based on experiments with terrestrial sediments that resemble Martian rocks. As reported by the working group in Nature Communications.She has found many signs of life in rocks from the Atacama Desert in Chile with the help of sensitive laboratory equipment. In contrast, results from instruments used on Mars today have remained close to or even below measurement limits — even if there are traces of life in the probe’s samples, the data is likely to remain murky at best.
The Atacama is the world’s oldest and driest desert and is so similar to Mars that NASA has been testing its Mars rovers since 1997. The similarities go further: the inhospitable region is home to a river delta more than 100 million years old. In many details, its red rocks resemble the river delta in Jezero crater, where the Mars probe Perseverance has been searching for signs of life since mid-2022. The difference is that the sediment known as redstone contains life to this day. Fog from the nearby ocean brings enough moisture to fuel the bacterial ecosystem. The team led by Azua-Bustos used highly sensitive laboratory methods to identify the DNA of these mysterious and often unknown microbes.
The ecosystem in the rock is the best that experts can hope to find on Mars: a few strange microbes, finely distributed, snatch the tiny presence out of the bare rock. If instruments on Mars probes are going to detect life on the Red Planet, they should, too, in the Atacama rocks. So the task force has been examining samples with the ground counterparts of the instruments installed on Curiosity’s rover and on the planned European ExoMars mission. Results are mixed at best. A gas chromatograph equivalent to the SAM instrument on Curiosity detected organics — but the instrument on Earth is 10 times more sensitive than its Martian counterpart, which probably wouldn’t have worked because of that. ExoMars’ MOMA instrument also failed due to the Atacama rock.
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