Recent research reveals that minuscule cracks within Martian minerals could serve as fleeting reservoirs for liquid water. Through the absorption of moisture from the atmosphere, hygroscopic salts might form ephemeral wet zones on Mars' surface.
Detecting liquid water on current Mars presents a significant challenge for planetary scientists. Although the planet is exceedingly arid today, orbital data has identified numerous sites containing hydrated minerals, indicating that water once interacted with the Martian surface.
Published in Science Direct, this study explores a novel mechanism that allows small quantities of liquid water to persist under present conditions. Instead of focusing on ancient aquatic features, the team examines microscopic spaces within minerals that could temporarily shelter water.
The concept hinges on the characteristics of hygroscopic salts, which can extract water vapor from Mars’ thin atmosphere. Under typical surface conditions, exposed liquid water would evaporate rapidly, but fractures in minerals may alter this outcome.
Martian Salts Extract Water Vapor from Atmosphere
Certain salts found on Mars have the ability to absorb humidity and generate thin liquid films on mineral surfaces when relative humidity rises. The researchers highlight calcium perchlorate as an example, capable of forming such solutions.
The team indicates that early mornings and late evenings are key periods, as humidity levels may become sufficiently high for these liquid layers to emerge. Rather than forming open water pools, moisture likely exists as microscopic films clinging to mineral surfaces. The article proposes that such water could migrate into tiny fissures inside salt crystals.
“the crystals could potentially provide transient liquid water to a hypothetical bacterium through an internal crack even during daytime dryness, making these locations a possible candidate environment for photosynthetic organisms on Mars today,” wrote the authors.
This phenomenon wouldn’t represent a large-scale underground water source, but rather small niches where liquid briefly appears surrounding mineral grains. Scientists are investigating if these niches might support microbial ecosystems.
Thermal Expansion Causes Mineral Cracks to Open and Seal
The investigation also examines how Martian temperature fluctuations influence mineral behavior. Daily heating and cooling induce expansion and contraction in mineral structures, generating mechanical stresses. At night, water vapor may condense and enter existing cracks, which then partly close as minerals expand with daytime warmth, effectively trapping moisture.
Previous computational analyses indicate that thermal stresses under Martian conditions are sufficient to initiate and gradually extend cracks. Factors such as mineral anisotropy, pre-existing fissures, and environmental conditions affect how these fractures behave.
The process does not create airtight seals; vapor movement through closed cracks remains possible, and the persistence of water depends on mineral responses to their surroundings.
Rethinking Martian Habitats for Liquid Water
This work offers a fresh perspective on where liquid water might still exist on present-day Mars. Instead of only seeking large bodies of ancient water, research can focus on tiny mineral-hosted microenvironments where moisture is transiently preserved.
Researchers describe these settings as microscale traps formed by interactions among salts, ambient humidity, and temperature cycles, aimed at determining if liquid water stays in contact with minerals during warmer intervals.
The scientists emphasize that their findings represent a conceptual framework rather than concrete evidence for life. This model proposes a plausible pathway for brief retention of liquid brines in one of the most arid environments within the Solar System.
“The present study should be regarded primarily as a conceptual feasibility analysis and hypothesis for transient near-surface brine retention within hygroscopic salt crystals under present-day Martian conditions,” said the authors.
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