Was there microscopic life on ancient Mars?

Was there microscopic life on ancient Mars?

NASA’s Curiosity Mars rover observed ancient soil cracks in a panorama of Mars called “Pontours,” which are believed to have formed during long cycles of wet and dry conditions over many years. Such cycles are believed to support the conditions in which life could have originated. A new paper suggests that the same conditions that created the Rift may have been favorable for the emergence of microscopic life.

Scientists don’t fully know how life began on Earth, but a prevailing theory holds that frequent cycles of wet and dry conditions on land helped assemble the complex chemical building blocks needed for microbial life.

The new paper, published in Nature, describes how the distinctive hexagonal pattern of these soil cracks provides the first evidence of wet-dry cycles that occurred on early Mars. These special soil cracks are formed when wet-dry conditions occur repeatedly, which may have been caused by weathering. This was stated by William Rapin of France’s Institut de Recherche en Astrophysique et Planetologie, the lead author of the research paper.

The rover drilled a sample in 2021 from a rock nicknamed “Pontours”. Then looked at clay cracks, a transitional zone between the clay-rich layer and its uppermost layer, which is rich in salty minerals called sulfates. While clay minerals usually form in water, sulfates form when water dries up.

The minerals prevalent in each zone represent different eras in the history of Gale Crater. The transitional zone between them represents a period when prolonged dry weather became prevalent and the lakes and rivers that once filled the crater began to subside.

“This is the first solid evidence we’ve seen that the ancient climate of Mars had such regular, Earth-like wet-dry cycles,” Rapin said. “But even more important is that wet-dry cycles are helpful—perhaps even necessary—for the molecular evolution that could lead to life.”

Although water is essential to life, a careful balance is needed – neither too much water, nor too little. The type of conditions that sustain microbial life – for example, those that can form a long-lasting lake. They are not the kind of conditions scientists think are necessary to promote the chemical reactions that could give rise to life. A major product of those chemical reactions are long chains of carbon-based molecules called polymers, including nucleic acids, molecules thought to be the chemical building blocks of life.

Image Credit: NASA/JPL-Caltech/MSSS/IRAP