Unexpected Discovery of Mud Cracks on Mars Raises Questions about Ancient Martian Conditions

Captured by NASA’s Curiosity Mars rover, a panorama of a region referred to as “Pontours” displays well-preserved ancient fissures in the mud. These fissures are believed to have been created over extensive periods through alternating wet and dry conditions. Scientists consider such conditions to be conducive for the formation of life. Credit: NASA/JPL-Caltech/MSSS/IRAP

Emerging research implies that the conditions causing these cracks may have been amenable to the development of microbial life forms.

Although the origins of life on Earth are not entirely clear, a widely accepted theory suggests that consistent cycles of wet and dry conditions on land facilitated the assembly of complex chemical components essential for microbial life. This makes the discovery of these ancient mud fissures by NASA’s Curiosity Mars rover especially compelling for researchers.

A recently published paper in the scientific journal Nature elaborates that the unique hexagonal formations of these mud cracks serve as the inaugural evidence of such wet-dry cycles on early Mars.

“Recurrent conditions of wetness and dryness, possibly on a seasonal basis, result in the formation of these specific mud cracks,” stated the paper’s principal author, William Rapin, from France’s Institut de Recherche en Astrophysique et Planétologie.

In-depth Exploration of Mount Sharp

The Curiosity rover is currently ascending through the sedimentary strata of Mount Sharp, which rises to a height of 3 miles (or 5 kilometers) within Gale Crater. The mud cracks were detected in 2021 after the rover drilled a sample from a geological feature named “Pontours,” situated within a transition zone between a layer abundant in clay and another one rich in salt minerals known as sulfates. Generally, clay minerals form in the presence of water, while sulfates are generated as water evaporates.

These minerals mirror diverse time periods in Gale Crater’s past. The transitional zone signifies a phase when extended dry periods became dominant, causing the lakes and rivers that formerly filled the crater to gradually diminish.

Detailed analysis of the panorama captured by Curiosity’s Mastcam at “Pontours” exposes hexagonal patterns, indicating that these mud cracks were a result of numerous cycles of wet and dry conditions over several years. Credit: NASA/JPL-Caltech/MSSS/IRAP

Deciphering Mud Crack Patterns

As mud dries, it contracts and breaks into T-shaped fissures, akin to what Curiosity previously observed at another site named “Old Soaker.” These T-shaped cracks confirm that the mud at Old Soaker dried just once. In contrast, the recurring exposure to moisture at Pontours altered these T-shaped junctions to Y-shaped ones, eventually leading to a hexagonal formation.

The hexagonal cracks persisted even when new sediment layers were deposited, confirming that the cyclic wet-dry conditions extended over a significant span of time. Curiosity’s precision laser instrument, ChemCam, corroborated a resilient crust of sulfates lining the edges of the cracks, which has contributed to their preservation over billions of years.

Implications for Understanding the Origins of Life

“Regular wet-dry cycles on ancient Mars provide the first tangible evidence of Earth-like climatic conditions,” stated Rapin. “These cycles are not merely conducive, but perhaps essential, for the molecular evolution that may culminate in life.”

While water is vital for life, a precise balance is necessary. Conditions that sustain microbial life, such as a long-lasting lake, differ from those believed necessary to catalyze chemical reactions potentially leading to life. Fundamental to such chemical reactions are long chains of carbon-based molecules known as polymers, which include nucleic acids considered as basic building blocks for life.

Cycles of wetness and dryness govern the chemical concentrations vital for the formation of polymers.

“The recent discoveries enrich the portfolio of findings by Curiosity,” commented the mission’s project scientist, Ashwin Vasavada, from NASA’s Jet Propulsion Laboratory in Southern California. “We’ve amassed substantial evidence suggesting ancient Mars could have sustained microbial life. Now we also have signs of conditions that might have aided the initiation of life.”

Mars as an Unparalleled Historical Record

The unearthing of Pontours mud cracks provides researchers with potentially their first chance to investigate the ancient conditions that may have been a crucible for life. Unlike Earth, where tectonic activities continually reshape the surface and obscure its prebiotic history, Mars lacks such tectonic plates, thereby preserving much older periods of its history.

“The presence of Mars in our celestial neighborhood, with its capacity to retain a record of natural processes possibly leading to life, fortuitously benefits us,” added Rapin.

For further insights into this groundbreaking discovery:

Source: “Sustained wet–dry cycling on early Mars” by W. Rapin, G. Dromart, B. C. Clark, J. Schieber, E. S. Kite, L. C. Kah, L. M. Thompson, O. Gasnault, J. Lasue, P.-Y. Meslin, P. J. Gasda and N. L. Lanza, published on 9 August 2023 in Nature.
DOI: 10.1038/s41586-023-06220-3

Additional Information on the Mission

The Curiosity rover was constructed by NASA’s Jet Propulsion Laboratory (JPL), overseen by the California Institute of Technology (Caltech) in Pasadena, California. The mission is directed by NASA’s Science Mission Directorate located in Washington, D.C.

Frequently Asked Questions (FAQs) about Mars Curiosity Rover Discovery

More about Mars Curiosity Rover Discovery

• NASA’s Official Page on Curiosity Rover
• Journal Nature’s Publication on the Discovery
• Institut de Recherche en Astrophysique et Planétologie
• NASA’s Mars Exploration Program
• The Gale Crater Research
• Understanding Wet-Dry Cycles and Life
• Space Exploration Technologies
• Chemical Building Blocks of Life
• More on Ancient Climates
• California Institute of Technology (Caltech)