Humidity Enhancement in Dry Permafrost: The Effects of Temperature Cycles on Habitability
Year: 2025
Type: article
Abstract: The search for life in the solar system often focuses on water and on environments where habitable conditions exist, persistently or occasionally. In this search, dry permafrost (ice-free frozen soil) has received minimal attention. It was previously proposed that within martian dry permafrost the water activity ( a w , an essential property for habitability) could be enhanced by diurnal thermal cycles and water desorption from soil grains, but the details remain unexplored. We examined a w in dry soil (which contained only vapor and adsorbed water) through experiments and numerical simulations and contrasted the results with a habitability threshold for terrestrial organisms ( a w > 0.6 ). We found that heating cycles in a soil raised a w . As water vapor desorbs from warming soil grains, it diffuses toward cooler adjacent soil, where a fraction of this incoming vapor enhances the local a w . In laboratory tests with loess and clay soils, we observed a w to increase by 0.06–0.12. Extrapolating from laboratory to permafrost conditions by using numerical simulations, we found that some Antarctic soils can be boosted periodically into a habitable range. In contrast, the current martian climate is too dry or cold for this a w -enhancement process to impact habitability. However, high-obliquity periods on Mars are analogous to the Antarctic case.
Source: Astrobiology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
OpenAlex ID: W4408944875