[Science Direct] This paper presents a conceptual model exploring a possible mechanism by which liquid water could potentially be maintained in direct contact with hypothetical microorganisms during warm daytime periods on Mars.
Hygroscopic salts detected on the surface are capable of binding water vapor from the atmosphere and creating a liquid solution, however during daytime they could dry out again if they have direct contact with the dry atmosphere.
In this work a model is presented, where crystalline fractures close after the cold and wet night, capturing the nighttime condensed liquid inside hygroscopic salt crystals for the daytime hours. In the evening and morning hours, the relative humidity can reach a level where, in the case of certain salts (e.g., Ca(ClO4)2), a thin surface liquid layer can form on mineral surfaces. Due to daily temperature fluctuations, the salts undergo significant thermal changes.
These mechanical stresses can lead to crack formation, which can be closed by daytime growth and then opened again by contraction during cooler nights. However, crack closure does not necessarily imply complete sealing, and the long-term retention of liquid water likely depends on additional thermo-mechanical factors and vapor transport conditions.
Previous numerical studies suggest that thermally induced stresses under Martian conditions may indeed be sufficient to support crack formation and subcritical crack growth; however, the detailed evolution of crack aperture likely depends on additional factors including mineral anisotropy, pre-existing microfractures, and local thermo-mechanical conditions.
Current water trapping micro-habitats on the surface of Mars, Science Direct (open access)
Astrobiology,
