Mars witnessed a periodic life friendly climate

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In a new piece of evidence suggesting that life on Mars was possible in the distant past, the rover "Curiosity" has discovered a fossil that indicates the red planet once had a cyclical climate with alternating periods of drought and moisture. This environment was similar to Earth's and conducive to the emergence of life, according to a study published on Wednesday.

While Mars currently possesses an extremely dry climate, it was home to many rivers and lakes billions of years ago, though these have since evaporated. Unlike Earth, Mars' surface hasn't been renewed through tectonic plates, and the traces of these ancient terrains have been well preserved.

Since 2012, the US space agency NASA's rover "Curiosity" has been exploring one such terrain, a massive crater called "Gale," along with its six-kilometer-high mountain composed of sedimentary layers.

In an interview with Agence France-Presse, William Rapin, a researcher at the French National Center for Scientific Research and the lead author of the study published in the journal "Nature," stated, "We quickly realized we were dealing with lake and river deposits, but we didn't know which specific type of climate was responsible for shaping them."

It's possible that Mars was either a frozen planet or a volcanic explosion caused its climate to become warm, leading to the formation of liquid water. This is according to a planetary scientist from the Institute for Research in Astrophysics and Planetology (University of Toulouse 3 - Paul Sabatier/French National Center for Scientific Research CNES) who conducted the study along with colleagues from the Lyon Geology Laboratory, as well as American and Canadian researchers.

While ascending the mountain slope, "Curiosity" encountered salt deposits that had formed within hexagon-shaped cracks in soil dating back to a period between 3.6 and 3.8 billion years ago.

Analysis of these deposits through the rover's American instrument "Mastcam" and the French-American instrument "ChemCam" revealed that these rocks consisted of dried mud cracks.

Rapin explained, "When the lake dries out, the mud cracks, but with the return of moisture, the mud resumes its natural state."

If this process repeated consistently, the cracks would accumulate to form hexagon-shaped patches, much like what is observed in ancient soil basins during seasonal droughts. A simulation of this process using mud from Earth, subjected to alternating wet and dry cycles, produced this hexagonal pattern "mathematically."

- From Stasis to Life -
The researcher affirms that these hexagonal formations represent "the first concrete evidence that Mars experienced cyclical climates." Just like on Earth, dry and wet seasons alternated in regular periods on Mars over three billion years ago. These periods lasted long enough, millions of years, for life to develop.

A similar climate is among the conditions necessary for organic material to transition from stasis to life. The French National Center for Scientific Research explained in a statement that the "Curiosity" rover had detected the presence of simple organic molecules that might have formed through geological or biological processes.

Among these molecules are amino acids that sometimes combine to create more complex molecules and form the basis of living organisms, such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). It's important to note that a similar process requires loops to form, as demonstrated by independent experiments conducted in labs, according to the French National Center for Scientific Research.

Rapin added, "In a severely dry world, there's no opportunity for these molecules to form, nor in an extremely humid one."

Thus, the Red Planet possessed the necessary equilibrium for the development of life forms. But what kind? Scientists propose the possibility of simple, single-celled microorganisms, such as bacteria or archaea, which are some of the earliest life forms on Earth.

However, the form in which these life forms appeared on Earth remains a mystery due to plate tectonics erasing traces of the earliest fossils. Rapin said, "What we lack on Earth is the story of the origin of life at the molecular level."

Nevertheless, the fossils on Mars offer humans the opportunity to understand on a smaller scale what happened during Earth's formation. As scientific missions, like "Curiosity" or "Perseverance," attempt to discover whether life forms did appear on Mars or have dissipated.