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Mars is not a place for humans. Mars is not a place at all. With its sunlit surface having been hit by radiation for millions of years, there is virtually no hope that anything (except perhaps a tardigrade) will survive in its reddish wastelands. But what’s underneath?
You don’t need to wander far from Earth to at least get an idea of what walking on the Red Planet would be like. The Atacama Desert in Chile is the driest place on the planet, seemingly lifeless, but wait. Most of the things that have adapted to such a hellish landscape hide in their lairs during the day and emerge at night. We may not find burrowing lizards on Mars, but the underground clay found in the Atacama Desert is teeming with microbes. Now scientists who have studied that clay believe it can tell us what to expect from similar clays that exist on Mars.
While Earth and Mars have some similarities other than Mars devoid of an atmosphere and any known life, there are some differences to be expected between Earth’s clays and alien things that NASA’s Perseverance and ESA’s Rosalind Franklin rover will probe. “Humidity and temperature are probably the biggest differences between the subsoil of the Earth and that of Mars. The Martian subsoil is much drier and colder, “Alberto Fairén, co-author of a study recently published in Scientific Reports, told SYFY WIRE.” Furthermore, the clays of Mars are by definition ancient and lithified, because the formation of clays requires the interaction of liquid water with primary minerals, and today there is no liquid water on Mars. “
So Perseverance may have to do with a search for microbes fossilized in stone. Lithification, or the gradual transformation of soil into rock, can occur over millennia as sediments build up and increased pressure on the lower layers shatters the grains together into what will eventually become stone. Sedimentary rocks are common in deserts (not to mention easy erosion), and Mars is essentially a desert planet, which means that what was once clay may be something closer to sandstone now.
This still doesn’t mean that wet clay doesn’t exist in some places below the surface. Also in the Atacama Desert, right here on our planet, is a recently discovered clay deposit that was previously unknown. Non-lithified soils are more likely to be habitable, or at least have been in the past, than clayey rocks. Fairén believes that, before Mars lost its atmosphere and was perhaps more Earth-like, shallow clays, just like those found a foot deep in the Atacama Desert, would have been habitable.
“The resulting lithified clays we are studying today are suitable reservoirs for biomarkers,” he said. “Therefore, the best chance of finding biomarkers for extinct life would be in lithified clays. A different story emerges if we look for the life that exists today. In my opinion, the best chance of finding existing life today would be in the near equatorial salt flats. “
Although scientists know what biomarkers to look for on Earth, they could end up being overlooked on Mars. We can only recognize life as we know it, but there is a possibility that if there ever was any kind of life form on Mars, they could have been life as we never imagined it.
“If we assume similar biology based on comparable building blocks (proteins, nucleic acids, lipids and everything that encompasses life as we know it), then we can extrapolate and imagine we could find comparable biomarkers on Mars,” Fairén said. “Otherwise, there is no way of knowing what would qualify as a biomarker, because we don’t know how life, if it existed, is or was on Mars.”
Both Perseverance and Rosalind Franklin are equipped with all kinds of scientific instruments that should be able to track biomarkers. The question is, depending on what Martian biomarkers actually are, will we recognize them or not.
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