Strange DNA found in desert offers lessons for hunting life on Mars


The Atacama Desert in Chile is the driest place on Earth. In spots, it looks like Mars. But even in the driest regions it is not lifeless. Using state-of-the-art equipment to study desert rocks, researchers have found DNA. Intriguing A mixture of microorganisms.

Astonishingly, 9 percent of the genetic fragments belong to species unknown to science, making them part of the “dark microbiome.” The report was released on Tuesday In the journal Nature Communications.

The organisms are bacteria that are “so strange and diverse,” the report says, that researchers can’t identify any known relatives.

“In almost half of the cases, the databases don’t tell us clearly what we have in our hands,” microbiologist Armando Azua-Bustos of the Center for Astrobiology in Madrid told The Post.

That brings him back to the Mars analogy: He and his scientific colleagues believe the Atacama is an ideal test bed for the search for life on Mars. But a similar search conducted with versions of the instruments on today’s Mars rovers failed to detect microbial signatures. That means that without bringing samples back to Earth, Azua-Bustos and her colleagues concluded that it would be difficult to find definitive evidence of current or past life in Martian soil.

The research appears to advance the long-term Mars exploration strategy of NASA and its partner the European Space Agency. They are in the midst of a multi-phase mission called Mars Sample Return. If all goes according to plan, samples of Martian soil obtained by NASA’s Perseverance rover, which just celebrated its second anniversary on Mars, will be hauled back to Earth early next decade for analysis in high-control laboratories.

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But this new research highlights the challenges facing scientists seeking to learn about the (hypothesized) biological history of Mars. Microbial life, especially if it’s extinct and long-fossilized, may be at or beyond the range that can be detected by instruments small enough to blast off into space and land on another planet.

Scientists have never found an example of extraterrestrial life, but a common assumption is that “habitable” worlds are inhabited—life could somehow, under the right conditions, emerge. The Red Planet has long fascinated astrophysicists. About 3 billion years ago, it looked like Earth when it had a thick atmosphere and liquid water on the surface. Conceivably, life on Mars is still mysterious, although astronomers would be delighted to find even a microscopic form that lived billions of years ago.

In 1976 NASA’s Viking mission carried out experiments designed to detect life, and one initially provided a promising signal, but most scientists concluded they had landed on sterile soil.

After the Viking mission, NASA has focused on finding and exploring sites that show evidence that Mars was habitable billions of years ago, when it was warmer and wetter. Perseverance and its still-active predecessor, the Curiosity rover, have found traces of organic molecules — molecules that are fundamental to life as we know it — on the surface, although this is no evidence of biological origins.

“The question remains whether they are meteorites, geological or biological,” said Amy Williams, a planetary scientist at the University of Florida and a member of the Curiosity and Persistence Science Groups.

The new report by Azua-Bustos and her collaborators is important because the preservation of organic material in a Martian-like environment is rare and would be difficult to detect with sophisticated laboratory instruments, Williams said.

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“This means that detecting organics with space probes like current and future Mars rovers may be an even bigger challenge because organics are readily broken down in the radiation-bathed Martian surface environment,” Williams said in an email.

However, the Atacama research shows that even in very arid environments there are layers of sedimentary rock that contain significant amounts of biological remains, said Chris House, a geologist and astrophysicist at Penn State. “It’s not really a surprise, but the results could have been uniformly bleak,” he said. That’s good news for scientists who hope that dry Martian rocks could yield traces of alien life.

Azua-Bustos is a native of the Atacama who spent years as a winemaker before becoming a scientist. He recalls growing up in a city in Chile where it rained only once a year and was always a highlight. He said there are places where residents have never seen rain in generations.

He said he regularly passes through a section of the desert known as the Red Stone on his way to a research site, and that it might be worth a closer look one day. The rocks were rust-red due to the presence of the mineral hematite, which is also responsible for Mars’ red color, he said.

100 million years ago, during the time of the dinosaurs, the Red Stone site was a river delta, similar to the Martian plateau within the diligently studied Jezero Crater.

Azua-Bustos was surprised to find genetic material of an unfamiliar nature found in the Atacama research. All life on Earth descends from a common ancestor – so far as we know. There has been speculation, particularly from scientist and author Paul Davies, that life may have appeared on Earth more than once and that there may still be a “shadow” biosphere that is so different that it doesn’t fit our definition of life on Earth.

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Azua-Bustos, however, defaults to a less spectacular interpretation of unclassified species: the genetic material of long-extinct and previously undocumented life forms.

The Perseverance rover continues to explore the Jezero Crater and dig up and store samples of Martian soil. The plan is to put another spacecraft on the surface, which will double as a launch pad. Perseverance will then deliver the samples to the lander, which will hurtle the object into orbit. There it will rendezvous with another vehicle, a European-built orbiter, that can carry precious cargo back to Earth. To analyze with the best laboratory equipment.

New research suggests it may be more effective — and possibly the only definitive — way to find out if there was ever life on Mars.

“We know there are things that need to be discovered,” Azua-Bustos said. “But if your instrument isn’t designed to detect those things, then we have a problem.”

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