Mars had a climate conducive to life, with a cycle of seasons similar to Earth’s – 09/08/2023 – Science

Mars at some point had a climate with cyclical seasons, conducive to the development of life, according to experts deducing from evidence found on the surface of the red planet by the rover Curiosity.

The planet, whose current climate is extremely arid, had abundant rivers and lakes billions of years ago, now evaporated.

Unlike Earth, the surface of Mars is not renewed by tectonic plate movements, and the deposits of these ancient soils have been perfectly preserved.

NASA’s Curiosity rover had been exploring one such site since 2012: the huge Gale crater and its 6,000-meter-high mountain, made of layers of sediment.

“We quickly understood that we were working on lake and river deposits, but we didn’t know what type of climate to link them to,” William Rapin, a CNRS researcher and lead author of a study published in Nature, told AFP.

Mars could have been an icy planet where a volcanic eruption suddenly warmed the atmosphere and caused liquid water to form, adds Rapin, a planetologist at the University of Toulouse III in France.

This specialist carried out the research together with the Lyon geology laboratory and American and Canadian colleagues.

As it slowly climbed the mountainside, Curiosity found hexagonal-shaped salt deposits in soil that dated between 3.8 to 3.6 billion years old.

Analysis of the rocks showed that they were cracks of dried mud.

“When a lake dries up, the mud cracks, and when it is rehydrated, the cracks ‘heal’,” explains William Rapin.

If this process is repeated regularly, the cracks organize themselves in such a way that they form hexagons, similar to patterns observed in ancient land basins that dry out seasonally.

Modeled earth mud subjected to dry and wet cycles further “mathematically” demonstrated this specific hexagonal formation.

from inert to live

This is the “first tangible proof that Mars had a cyclical climate”, according to the researcher.

Like Earth, the dry and wet seasons followed each other at regular intervals for more than three billion years, and for long enough, several million years, for life to appear.

Such a climate is one of the conditions for organic matter to pass from inert to living.

“Curiosity had already detected the presence of simple organic molecules that can be formed by geological and biological processes”, details the French scientific research center CNRS in a press release.

Amino acids, for example, which sometimes combine to form more complex and constitutive molecules of living organisms, such as RNA and DNA. Such a process, however, needs cycles to form, as independent experiments in the laboratory have demonstrated.

“In a very dry world, these molecules never have the opportunity to form; in a very humid world, neither”, adds the planetologist.

Therefore, the red planet had the necessary balance for the development of life forms.

What kind? Scientists think of primitive single-celled microorganisms like those in the kingdom archaea and bacteria, which are our most ancient ancestors.

But how they appeared on Earth remains a mystery, as plate tectonics have erased the traces of the oldest remains.

“What we don’t know on Earth is the odyssey of the origins of life at the molecular level”, comments William Rapin.

Mars, however, kept a record, which could allow us to understand on a small scale what happened to our planet in its infancy. Although, at the moment, it is not known if any kind of life actually flourished on the red planet, or if it died trying.