Dry Valleys Of Antarctica Research Articles

Are there carbonate deposits in the Valles Marineris, Mars?

The thick sequences of layered deposits found in the Valles Marineris have recently been determined by S. S. Nedell, S. W. Squyres, and D. W. Andersen (1987, Icarus, 70, 409–441) to contain a minimum of ∼ 10 5 km 3 of material. We suggest that this material could be derived from the precipitation of 30 mbar of atmospheric CO 2 as carbonates in lakes. As surface temperatures fell on Mars, the presence of an insulating ice cover would have allowed liquid water to exist, fed by transitory surface melting. Atmospheric CO 2 would have accumulated in such lakes enhancing carbonate precipitation. Support for this hypothesis comes from processes that occur in the perennially frozen lakes in the dry valleys of Antarctica where the mean temperature is 253°K and the lake water is supersaturated with atmospheric gases. A search of the recently reissued Mariner 6/7 infrared spectrometer data in the wavelength region between 2 and 6 μm failed to confirm the presence of carbonates. Due to the fact that no spectral footprints appear to directly overlie the layered deposits, and that deposits may be blanketed by an eolian mantle, this negative result is inconclusive. We feel that the canyon deposits are still a prime site for future searches for carbonates on Mars.

Radiocarbon Dating with the University of Washington Accelerator Mass Spectrometry System

The University of Washington FN tandem accelerator mass spectrometry (AMS) system has been used in a series of 14C studies. 1) The 14C concentrations in annual growth rings for 1962, 1963, and 1964 of a Sitka spruce, each divided into ten sequential segments, were measured; a full and rapid response of tree-ring cellulose to atmospheric changes in 14CO2 is indicated, with a delay, if any, of not more than three weeks. 2) The C concentrations in two chemical fractions of dissolved organic carbon and in two fractions (by size) of particulate organic carbon were measured for Amazon River samples from several locations. All contain bomb carbon, but the amounts differ significantly. 3) Algae samples from lakes in the dry valleys of Antarctica were dated in order to assist in the reconstruction of the climatic history of Antarctica. 4) Background studies indicate that the contribution of the AMS system itself to the observed 14C concentrations is equivalent to an age of ca 60,000 14C yr BP; for a prepared sample of 5mg of carbon the background corresponds to ca 50,000 years.

Chemical weathering and diagenesis of a cold desert soil from Wright Valley, Antarctica: An analog of Martian weathering processes

Weathering, diagenesis, and chemical alteration of a soil profile from the Dry Valleys of Antarctica have been studied as an analog to soil development within the Martian regolith. Soil samples from a one‐meter‐deep soil pit on Prospect Mesa, Wright Valley, have been examined for their major element concentrations, water soluble cations and anions, carbon, sulfur, and water concentrations, and related petrographic characteristics of weathering in a cold, dry environment. Petrographic study of the soil samples indicates that most silicate mineral and lithic fragments exhibit some degree of alteration. Chemical alteration occurs in samples both from above and from within the permanently frozen zone. Concentrations of water soluble cations (Na+, K+, Ca2+) and anions (Cl−, SO42−, NO3−) decrease significantly from the surface to the permanently frozen zone, suggesting major movement of water soluble species. Enrichments in secondary mineral abundances correlate with the water soluble ion concentrations. Formation of zeolites is observed throughout the soil column and may be potential reservoirs for volatile storage within the regolith. From the detailed study of the Dry Valley soils, an idealized soil profile for the regolith has been developed and is suggested as applicable to other planetary surfaces, especially the Martian nearsurface environment. The soil profile consists of four zones: aeolian, salt, active, and permanently frozen.

The evolution of Antarctic yeasts: DNA base composition and DNA–DNA homology

The 16 biotypes of the Cryptococcus vishniacii complex of anamorphic yeasts (Basidioblastomycetes), unique to the Dry Valleys of Antarctica, include seven species separated by DNA–DNA homologies of less than 52%. Since species belonging to the complex can be as distantly related as C. bhutanensis (a Himalayan yeast, guanine + cytosine (G + C) 54.18 mol%) is to these species, a common ancestor probably originated and speciated outside of the Dry Valleys. The species C. vishniacii (G + C 54.52–55.48 mol%) comprises seven varieties with greater than 59% DNA–DNA homology and must therefore have been established in the Dry Valleys long enough to have evolved these divergent genomes. In the C. vishniacii complex, G + C values differing by more than 1 mol% are accompanied by DNA–DNA homologies of less than 23%.

Evidence of an Indigenous Microbiota (Yeast) in the Dry Valleys of Antarctica

SUMMARY: Soil samples from sites in the Dry Valleys of South Victoria Land, Antarctica, similar to some sites previously considered abiotic, contained a variety of microbes. The fungi recovered included Tilletiopsis washingtonensis, Sporobolomyces holsaticus, Sp. roseus (all previously unreported from Antarctica), Cryptococcus laurentii var. laurentii and Cr. vishniacii, as well as some unremarkable filamentous fungi imperfecti. Cryptococcus vishniacii occurs only in these soils, has a distribution suggesting indigenous origin and shows appropriate psychrophilic character and energy requirements for life in this highly stressed environment. Populations of Cr. vishniacii cloned and grown at 4 °C are heterogeneous in temperature response, some cells being capable of growth at 20 °C or 23 °C with loss of the ability to assimilate succinate or citrate. Cryptococcus vishniacii and endolithic cyano-bacteria could constitute a minimal community in Dry Valley soils.

An upper Paleozoic tillite in the Dry Valleys, south Victoria Land, Antarctica

ABSTRACT A thin pebbly mudstone unit which lies on a Devonian-Permian disconformity at Mount Feather and Mount Fleming in the Dry Valleys of Antarctica is interpreted as a glacial-fluvial deposit and is correlated with Upper Paleozoic tillites farther to the south. These glacial beds are composed of two lithologies: mudstone (till) and channel sandstones (water-laid sands). This marks the northernmost known exposure of Paleozoic tillites in Victoria Land.