Article by: Andacs Robert Eugen, on 11 August 2023, at 01:38 am PDT

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Scientists are still trying to understand how life on Earth began, and one theory is that wet and dry cycles on the planet helped create the necessary chemical precursors for microbial life. Recently, NASA's Curiosity rover discovered a set of ancient, well-preserved mud fissures on Mars, which researchers believe are evidence of similar wet and dry cycles on the planet. 

In an article published in the prestigious journal Nature, French researcher William Rapin explains that the hexagonal pattern in the mud fissures indicates a seasonal cycle of wet and dry conditions. Curiosity discovered these mud fissures in 2021 during its ascent of Mount Sharp within Gale Crater after sampling a rocky target called "Contours."

The area between the clay-rich layer and the sulfate-rich layer where Contours was found reveals how the mineral composition of the site changed over time. As the lakes and rivers in the crater dried up, the mud contracted, leaving behind T-shaped crossroads that eventually transformed into Y-shaped and hexagonal patterns due to recurring moisture.

The hexagonal cracks in this middle realm continued to form despite the addition of new layers of sediment. This persistent formation highlights the ongoing cycle between wet and dry conditions over an extended period. The laser instrument ChemCam on Curiosity confirmed the presence of solid sulfate deposits around the edges of the cracks. This discovery is not surprising, given the adjacent area is rich in sulfates. The salty coating was essential in protecting the mud cracks from erosion, preserving their original state for eons.

The findings have implications beyond their geological significance. Rapin suggests, "This is the first tangible evidence of Mars' ancient climate oscillating in a rhythm similar to Earth's wet-dry cycles. Furthermore, these climatic fluctuations could have been a catalyst, if not a prerequisite, for the complex molecular evolution necessary for life."

While it is undeniable that water is crucial to the formation of life, the key takeaway is the need for a delicate balance - not too much and not too little water. Conditions that foster microbial life differ from those that encourage the chemical interactions that lead to forming life's building blocks, such as nucleic acids.

The alternating wet and dry cycles dictate the concentration of the chemical entities that fuel the reactions leading to polymer synthesis.

Ashwin Vasavada, the project scientist overseeing Curiosity's mission from NASA's Jet Propulsion Laboratory in Southern California, describes the discovery as a significant scientific breakthrough. He states, "Curiosity's discoveries have been extensive over the past 11 years, providing compelling evidence that Mars has the potential to support microbial life. At this point, the mission is uncovering the atmospheric dynamics that may have played a role in the origin of life."

The discovery of the Pontours mud cracks provides scientists with a glimpse into the primordial origins of life. The lithosphere's continuous movements on Earth conceal traces of its pre-biotic history. In contrast, Mars' lack of tectonic activity preserves relics from its past, encapsulating remnants from different stages of its history.

In Rapin's musings, there is a sense of gratitude for the opportunity to study Mars. "We are fortunate to have a celestial neighbor like Mars, which preserves a narrative of the elemental forces that may have led to the formation of life."