Exobiological aspects of mass transfer in microzones of permafrost deposits

Abstract

The possibility of long-term survival of viable microorganisms in permafrost on other plants and on asteroids is inferred from physical and chemical conditions in dispersed frozen systems. An important factor for long-term survival of microorganisms in dispersed systems at temperatures below 0°C is the transfer of unfrozen liquid water and ions. Our experimental data show that mass exchange in frozen rocks is greatest in microzones with low ice content and high chemical potential gradients. Ion diffusion coefficients there are greater that 10 −10 m 2/s. These microzones are localized close to ice inclusions (schlierens, lenses, veins). Material with high ice content, on the other hand, is characterized by very low transfer coefficients (ion diffusion less than 10 −16 m 2/s). The occurrence of highly permeable microzones in permafrost supports the hypothesis that mass transfer there could result in exchange of liquid water and ions between living cells and the habitat, permitting metabolism. Highly permeable microzones in frozen rocks are the areas in permafrost most likely to support viable microorganisms in the active state on Earth, on cold planets, and on asteroids.