Arctic / Antarctic / Alpine

Humidity Enhancement in Dry Permafrost: The Effects of Temperature Cycles on Habitability

By Keith Cowing
Status Report
Astrobiology via PubMed
April 21, 2025
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Humidity Enhancement in Dry Permafrost: The Effects of Temperature Cycles on Habitability
McMurdo Dry Valleys, Antarctica. — NASA

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 ( ๐‘Ž๐‘ค, 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 ๐‘Ž๐‘ค 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 ( ๐‘Ž๐‘คโ€‰โ€‰>โ€‰โ€‰0.6). We found that heating cycles in a soil raised ๐‘Ž๐‘ค.

As water vapor desorbs from warming soil grains, it diffuses toward cooler adjacent soil, where a fraction of this incoming vapor enhances the local ๐‘Ž๐‘ค. In laboratory tests with loess and clay soils, we observed ๐‘Ž๐‘ค to increase by 0.06โ€“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 ๐‘Ž๐‘ค-enhancement process to impact habitability. However, high-obliquity periods on Mars are analogous to the Antarctic case.

Humidity Enhancement in Dry Permafrost: The Effects of Temperature Cycles on Habitability
Astrobiology via PubMed

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Naโ€™Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) ๐Ÿ––๐Ÿป