Exploring Mars' Ancient Hydroclimate: Evidence of Life?

 Mars showcases an impeccably conserved sedimentary record that spans back 4.3 billion years, or perhaps even longer. It's well documented that the planet initially boasted habitable and consistently moist surface environments. However, knowledge about transient and probable cyclical early hydroclimatic patterns remains sparse. Post-deposition processes, typically triggered by short-term hydroclimatic regime shifts, often leave surface marks such as mud cracks. Despite their susceptibility to erosion, these surface traces are crucial to comprehend past surface environments.

Broadly, varying models of early Mars' water cycle, its seasonality, and sporadic dryness remain inadequately defined. Dr. Nina Lanza, principal investigator of the ChemCam instrument aboard the Curiosity rover, said, "Intriguing new discoveries of mud crack patterns are helping us piece together the incomplete account of water on Mars."

Curiosity has now transitioned into a new area abundant with sulfates after years of investigating silicate-rich soils, signifying a crucial environmental shift. In this new environment, Dr. Lanza and her team noticed a change in mud crack patterns, indicating a shift in the surface drying process. This suggests that water on Mars' surface was present in a cyclical manner - it would persist for some time, evaporate, and the process would repeat until mud cracks or polygons formed. Dr. Patrick Gasda from Los Alamos National Laboratory said, "One of the critical objectives of the Curiosity mission and the rationale behind selecting Gale Crater was to understand the transformation from an ancient Mars with a warm, wet climate to the current cold, dry Mars."

The rover discovered that the mud cracks were only a few inches deep, implying that the wet-dry cycles could have been seasonal or even more abrupt, similar to flash floods. These findings suggest that Mars once had a climate similar to Earth's, with seasonal or short-term floods, and could have been hospitable to life at some point. Dr. Gasda added, "This phenomenon is crucial as it is an ideal site for the formation of life-essential polymeric molecules, including proteins and RNA, provided the right organic molecules were present."

The team's research was published in the journal Nature this week.