The Atacama Desert's hardy aerobic microbial populations have been found to occupy ecological niches substantially different from those occupied by aerobic micro-organisms in the California and Valley of 10 000 Smokes deserts. Two specialized groups of microflora, the actinomycetes and micro-aerophiles, appear to be abundant in some portions of the Atacama Desert, though many of the bacterial and mold types and species common in the California deserts are absent. The factors defining the ecological niches and relationships of microbial populations in these soils are largely unknown. In several respects, moreover, micro-environments in these soils are similar to some of those expected on Mars. For the purpose of establishing the engineering constraints on the design of life detection instruments and their sampling and processing components, the nature and diversity of species of micro-organisms prevalent in the soils of extremely dry climates of the earth have not been adequately investigated. Useful ecological information about these soils will include an estimate of the likely lower limit in numbers or mass of viable aggregates in the autochthonous populations and the survivability of these populations under mechanical processing and isolated storage. Knowledge of the artificial niches, growth media for example, which members of these populations accept, will be useful in designing life detection instruments themselves. The range of practical designs for soil sampling devices will be determined by the nature of the particles and surfaces, and their depths, on which various physiological groups or largest populations of micro-organisms reside in the extremely dry deserts of the earth. The results of several exploratory experiments are used to provide some understanding of the environment and the ecological patterns of micro-organisms in soils of the earth's driest deserts.