For many years, the extreme environment of the Antarctic Dry Valleys was thought to play host to just a few viable microorganisms. However, as Cary and colleagues explain, recent work has led to the identification of a complex community structure that is able to survive in one of the coldest and driest places on Earth. The arid soils of the Antarctic Dry Valleys constitute some of the oldest, coldest, driest and most oligotrophic soils on Earth. Early studies suggested that the Dry Valley soils contained, at best, very low levels of viable microbiota. However, recent applications of molecular methods have revealed a dramatically contrasting picture — a very wide diversity of microbial taxa, many of which are uncultured and taxonomically unique, and a community that seems to be structured solely by abiotic processes. Here we review our understanding of these extreme Antarctic terrestrial microbial communities, with particular emphasis on the factors that are involved in their development, distribution and maintenance in these cold desert environments.

On the rocks: the microbiology of Antarctic Dry Valley soils.

Two surface samples collected from the Chryse Planitia region of Mars were heated to temperatures up to 500 degrees C, and the volatiles that they evolved were analyzed with a gas chromatograph-mass spectrometer. Only water and carbon dioxide were detected. This implies that organic compounds have not accumulated to the extent that individual components could be detected at levels of a few parts in 10(9) by weight in our samples. Proposed mechanisms for the accumulation and destruction of organic compounds are discussed in the light of this limit.

Search for organic and volatile inorganic compounds in two surface samples from the chryse planitia region of Mars.

The dry valleys of South Victoria Land, Antarctica, together with a few other ice-free areas on the perimeter
of the Antarctic continent, form what is generally considered to be the most extreme cold-desert region of the earth. During the past S years, we have been interested in the dry valleys as a model environment for investigating questions connected with the biological exploration
o£ Mars. The extraordinary aridity of the region, its low temperature, and its geographical isolation give it a quasimartian character, although it is to be
understood that the actual martian environment is still more hostile than that of the valleys. With our associates, we have investigated the kinds, numbers, and distribution of soil microorganisms in the valleys in order to gain insight into the practical problems of searching for life in an extreme environment. Detailed results of these studies have been published by Cameron and co-workers (1-5). In this-article, we review the major findings of our own and of other groups of investigators in this region,
especially as they apply to martian exploration.

https://science.sciencemag.org/content/sci/176/4032/242.full.pdf

Microbiology of the dry valleys of antarctica.

If the science of microbiology is approaching maturity, then Antarctic microbiology is only just emerging from its infancy. The early expeditions of the 20th century used classical medical methodology to isolate and identify bacteria, yeasts, and fungi from sea water, soil, snow, air, and animals (Ekelof, 1908; Tsiklinsky, 1908; Gazert, 1912; McLean, 1918, 1919). The initial emphasis was on survey and taxonomy, although Gazert (1912) noted the influence of marine bacteria on nutrient cycling during the German Antarctic Expedition of 1901–03. However, it is Ekelof of the Swedish National Antarctic Expedition 1901–03 who may be regarded as the father of Antarctic microbial ecology. Between February 1902 and November 1903, he made a seasonal study of the soil and air microbiota at Snow Hill Island (64° 30′S) off the east coast of the Antarctic Peninsula (Fig. 1). Using rich medical media, he monitored viable bacteria, yeasts, and other microfungi but made no mention of the organisms resembling cyanobacteria and microalgae which are frequently the dominant primary producers in terrestrial Antarctic ecosystems (Ekelof, 1908).

Ecological Aspects of Antarctic Microbiology

The failure of Viking Lander thermal volatilization (TV) (without or with thermal degradation)–gas chromatography (GC)–MS experiments to detect organics suggests chemical rather than biological interpretations for the reactivity of the martian soil. Here, we report that TV–GC–MS may be blind to low levels of organics on Mars. A comparison between TV–GC–MS and total organics has been conducted for a variety of Mars analog soils. In the Antarctic Dry Valleys and the Atacama and Libyan Deserts we find 10–90 μg of refractory or graphitic carbon per gram of soil, which would have been undetectable by the Viking TV–GC–MS. In iron-containing soils (jarosites from Rio Tinto and Panoche Valley) and the Mars simulant (palogonite), oxidation of the organic material to carbon dioxide (CO2) by iron oxides and/or their salts drastically attenuates the detection of organics. The release of 50–700 ppm of CO2 by TV–GC–MS in the Viking analysis may indicate that an oxidation of organic material took place. Therefore, the martian surface could have several orders of magnitude more organics than the stated Viking detection limit. Because of the simplicity of sample handling, TV–GC–MS is still considered the standard method for organic detection on future Mars missions. We suggest that the design of future organic instruments for Mars should include other methods to be able to detect extinct and/or extant life.

https://www.pnas.org/content/pnas/103/44/16089.full.pdf

The limitations on organic detection in Mars-like soils by thermal volatilization-gas chromatography-MS and their implications for the Viking results.

Soils from the dry-valley region of Antarctica can be sterile by the usual microbiological criteria and yet contain significant amounts of organic carbon Examination of one such soil shows that the organic material is finely divided anthracite coal These findings have significant implications for the biological exploration of Mars

G. P. Shulman

Papers

Sterile Soil from Antarctica - Organic Analysis