Was there life on Mars? Stunning discovery raises excitement

Scientists have discovered evidence of ancient wet-dry cycles on Mars, which could have been conducive to the emergence of life.

The findings were published in a recent paper in Nature and are based on data from NASA's Curiosity Mars rover.

The rover found a patchwork of well-preserved ancient mud cracks with a distinctive hexagonal pattern. These cracks are believed to be the first evidence of wet-dry cycles on early Mars.

These cycles are thought to have played a crucial role in the formation of life on Earth by helping to assemble the complex chemical building blocks necessary for microbial life.

"These particular mud cracks form when wet-dry conditions occur repeatedly – perhaps seasonally," said the paper’s lead author, William Rapin of France’s Institut de Recherche en Astrophysique et Planétologie.

The discovery was made in a transitional zone between a clay-rich layer and a higher layer enriched with salty minerals called sulfates. As mud dries out, it shrinks and fractures, forming T-shaped junctions.

However, recurring exposures to water caused these junctions to soften and become Y-shaped, eventually forming a hexagonal pattern.

The hexagonal cracks in the transitional zone kept forming even as new sediment was deposited, indicating that the wet-dry conditions continued over long periods of time. A crust of sulfates along the cracks' edges, confirmed by Curiosity's precision laser instrument, ChemCam, made the mud cracks resistant to erosion, preserving them for billions of years.

"This is the first tangible 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 – maybe even required – for the molecular evolution that could lead to life."

Although water is essential to life, a careful balance is needed. Wet-dry cycles control the concentration of chemicals that feed the fundamental reactions leading to the formation of polymers, long chains of carbon-based molecules considered to be chemical buildings blocks of life.

The discovery of the Pontours mud cracks may have provided scientists their first opportunity to study the remains of life’s cauldron. Unlike Earth, Mars doesn't have tectonic plates, so much older periods of the planet’s history have been preserved.

"It’s pretty lucky of us to have a planet like Mars nearby that still holds a memory of the natural processes which may have led to life," Rapin said.