Salt deliquescence along boulder cracks in the Antarctic Dry Valleys: An overlooked source of moisture for rock weathering processes

Cracking is a primary rock-weathering mechanism in arid environments, where dry conditions typically limit the efficacy of water-driven weathering processes. Here, we present results from a field-based experiment in the hyper-arid and frigid Antarctic Dry Valleys (ADV) that documented recurring periods of transient accumulation of liquid water along rock cracks during otherwise dry conditions. This moisture was likely sourced from the deliquescence of hygroscopic salts during sub-saturated humidity conditions. Analysis of meteorological data from 17 stations scattered throughout the ADV revealed that near-surface atmospheric conditions across one of Earth's driest environments can annually support tens of deliquescence-efflorescence cycles of hygroscopic salts, such as, CaCl₂, NaNO₃, NaCl, and MgCl₂. This deliquesced moisture may have an important role in the cracking processes of ADV rocks. In a broader context, the results from the ADV suggest that deliquesced atmospheric humidity may be an overlooked source of moisture available for rock weathering processes in otherwise extremely dry deserts on Earth and possibly Mars.