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Recent scientific research in Chile’s Salar de Pajonales has revealed that gypsum deposits can act as microscopic shields, protecting living microbes and preserving ancient fossils. The findings hold major implications for astrobiology and the ongoing search for life on Mars, as similar mineral formations exist on the Martian surface.

Geographical and Environmental Profile

Salar de Pajonales is a large playa (salt flat) located in northern Chile on the western margin of the Altiplano-Puna plateau, at an elevation of approximately 3,500 metres above sea level. It is the third-largest salar in the Atacama Region, after Salar de Atacama and Salar de Punta Negra.

The region lies within the hyper-arid core of the Atacama Desert, one of the driest places on Earth.

Polyextreme Conditions

The site experiences polyextreme environmental conditions, including:

• Extreme aridity
• High altitude and low atmospheric pressure
• Intense solar and ultraviolet radiation
• Large diurnal temperature variations
• Sulfate-rich mineral composition

These characteristics closely resemble surface conditions on Mars, making the region a significant Martian analogue site.

Hydrological and Geological Features

Salar de Pajonales is an endorheic basin (a closed drainage system with no outflow), sustained primarily by groundwater inputs.

The surface is dominated by evaporitic deposits, particularly:

• Gypsum (calcium sulfate dihydrate) crusts
• Layered microbial structures known as stromatolites

These mineral and biological structures provide a natural laboratory to study life under extreme conditions.

Gypsum as a Microbial Shield

Recent studies have demonstrated that gypsum acts as a microscopic protective barrier.

Key Findings

• Active extremophile communities: Halophilic bacteria and archaea survive within protected microhabitats inside gypsum crystals.
• Preserved fossilized microbes
  • Ancient microbial remains and molecular biosignatures are trapped within gypsum layers.
  • Some biosignatures date back thousands of years.
• Radiation and Desiccation Protection
  • Gypsum shields biological material from ultraviolet radiation.
  • It prevents rapid dehydration in hyper-arid conditions.

Thus, gypsum serves as a natural repository of biosignatures, preserving evidence of life even in extreme environments.

Astrobiological Significance

The environmental conditions in Salar de Pajonales mirror those believed to have existed on early Mars. Importantly, gypsum has also been detected on Mars by orbital and rover missions.

The study suggests that:

• Future Mars missions should prioritize gypsum-rich terrains.
• Orbiters and rovers can target sulfate deposits as prime candidates for detecting ancient life.
• Mineralogical mapping can guide astrobiological exploration strategies.

This research strengthens the hypothesis that if microbial life ever existed on Mars, its traces may be preserved within evaporitic minerals like gypsum.