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Why signs of life on Mars remain a big mystery

living in mars

By svocal02Published 2 years ago 4 min read
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Why signs of life on Mars remain a big mystery
Photo by Nicolas Lobos on Unsplash

For scientists searching for extraterrestrial life forms, it's becoming hard to ignore the song of the Martian sirens. Recent observations made by rovers on the red planet suggest the signature of microbes, does this mean that the Earth is not the only refuge of life in the solar system?

A few weeks ago, NASA shared encouraging news: the Curiosity rover observed a mixture of carbon isotopes in the rocks of the Gale crater which, on Earth, would be a sign of life. The vehicle also recorded both random and seasonal spikes in methane, a gas primarily produced biologically on Earth.

About 3,700 km away, NASA's newest rover, Perseverance, captured strange purple films on the rocks littering the floor of Jezero Crater. This type of coating is widespread on the red planet and resembles the desert varnishes found on Earth in the presence of microbes.

For the moment, scientists are not ready to affirm that our scarlet neighbor was ever inhabited. Each clue evoking biology could also be explained by a still unknown aspect of Martian geology or chemistry, that is to say how little we know about the functioning of this planet: what we perceive as the imprints of life could be the result of inert phenomena.

"We're looking at an extraterrestrial world, we probably haven't thought of everything," said Abigail Fraeman, deputy Curiosity project scientist for NASA's Jet Propulsion Laboratory.

The next step in our quest for Martian life forms will be to repatriate pieces of the planet to the laboratory on Earth, where the most powerful instruments at our disposal will be able to search for the answers to the question that has occupied humanity since the night of the time. The Perseverance rover is already busy collecting the first samples that may contain evidence of the presence of microorganisms in Jezero Crater billions of years ago.

Whatever the answer, it will give us valuable information about the origins of life on our own planet.

"The ancient history of the two planets has many similarities, it makes you wonder why they then evolved so differently," says astrobiologist Amy Williams of the University of Florida. “If there is no life on Mars, then why? What changed ? And if there ever was, what happened to him? »

FROM ZIGGY TO CURIOSITY

In our imagination, Mars has almost always been inhabited, sometimes by extraterrestrials, sometimes by our future colonies. Unfortunately, human-sent probes quickly destroyed dreams of advanced civilization, seasonal vegetation, or even small, defenseless gelatinous vegetarian beings.

"There's nothing fluorescent, nothing that says hello, and you don't need a laser gun to land on it," jokes Andrew Steele of the Carnegie Institution for Science.

Aerial imagery and surface experiments conducted by NASA's Viking landers clearly indicated that Mars was not a planet teeming with easily detectable life. "It took a long time for Mars research to recover from that finding," Steele said.

In 1996, scientists announced the discovery of a Martian meteorite in the Allan Hills region of Antarctica. This meteorite appeared to contain worm-shaped microfossils, possibly the mineralized remnants of a life form that writhed on the planet's surface 4.1 billion years earlier. These observations were ambiguous and extremely divisive, so debates surrounding the discovery continue today. But you have to look on the bright side of things.

"The Allan Hills controversy really advanced astrobiology," said Kennda Lynch, astrobiologist at the Lunar and Planetary Institute. “We owe a lot to this meteorite, because it really forced us to reconsider what we knew about life. »

A few weeks ago, Steele and his colleagues declared that the complex organic compounds discovered in ALH84001 had formed without the help of life, but by ordinary chemical reactions caused by the meeting of underground fluids, rock and minerals. .

“Does this mean that this meteorite does not contain Martian life? No, I can't prove it,” Steele replies. “If there is a Martian organism in this rock, it doesn't show us anything similar to terrestrial organisms. It's something totally different, and I keep looking for it. »

Could such geological reactions be the source of Martian methane? Or organic matter that litters the planet? Or dandruff from Jezero Crater? It is quite possible, answer the astrobiologists. Mars is another world, a place of strange chemistry and landscapes that, while reminding us of Earth, are no less alien.

“Mars has once again demonstrated that it is not Earth. It's not a primitive version of the Earth frozen in time,” Williams says. “It's a planet in its own right with its own evolution; Earth-like processes are still going on there, and other decidedly alien ones. »

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