V. Ya. Lipenkov

Microflora in the basal strata at Antarctic ice core above the Vostok lake

The microbiological investigations of the Antarctic ice core at the Vostok station become especially important in connection with the discovery of an subglacial lake in this region. This lake is considered by the world-wide scientific community to be an important object for searching for relict forms of life on the Earth and also as a model for solving a number of problems of exobiology--for instance for development of methods to penetrate into underice sea at Europe--Jupiters satellite. For the first time the Antarctic ice core samples were taken from the horizons which correspond to the basal zone (3534-3541 m) and to the accreation ice zone (3555-3611 m) above the subglacial lake Vostok. As a result of the microbiological investigations it was shown that the total number of microbial cells have been in the same range of quantities as at the upper, younger horizons and varied from 1.3 x 10(2) up to 9.6 x 10(2) cl/ml. Some periodicity in the cell concentration and in their morphological diversity was revealed along the core. The maximal number and the greatest morphological variety were detected at horizons with the depth of 3534, 3555 and 3595 m. A drop in the cell concentration two or three times as much was found in ice layers under each of the above mentioned horizons. The discovered stratification is apparently connected with the periodicity of the lake water interactions with the basal ice layer and obviously depends on the complex natural events which took place in the geological history of our planet.

What is the deepest part of the Vostok ice core telling us

Abstract This review paper is mainly concerned with a geochemical investigation of the deepest part of the Vostok ice core between 3310 m, the depth at which the palaeoenvironmental record present in the ice above is lost, and the bottom of the core about 130 m above subglacial Lake Vostok. Two sections constitute this part of the core. The upper section (3310–3539 m depth) still consists of ice of meteoric origin but subjected to widespread complex deformation. This deformation is analysed in light of a δD–deuterium excess diagram and information on microparticles, crystal sizes and chemical elements distributions in that part of the core. Such ice deformation occurred when the ice was still grounded upstream from Vostok station in a region with subfreezing temperatures. The lower section from 3539 m to the bottom of the core at 3623 m depth is lake ice formed by freezing of subglacial Lake Vostok waters. This is indicated by the isotopic properties (δD, δ18O and deuterium excess), by electrical conductivity measurements (ECM), crystallography and gas content of the ice. These ice core data together with data on ionic chemistry favour an origin of the lake ice by frazil ice generation in a supercooled (below pressure melting point) water plume existing in the lake followed by accretion and consolidation by subsequent freezing of the host water. The helium profile of this deepest part of the Vostok core is quite unusual and surprising. It has important implications for the interactions between the ice sheet and the lake. Two constrasting scenarios can be satisfactorily constructed so that the lake residence time is not well constrained.

Antarctic ice sheet as an object for solving some methodological problems of exobiology

Abstract Icy formations are often found in the cosmos: there are comets nuclei, polar caps of Mars and of other planets and Europa, the Jupiters satellite covered with icy crust. Various inclusions of mineral and organic compounds have been permanently accumulated in the ice thickness which protects them from subsequent environmental influence and ensures their reliable and long-term preservation. So icy bodies are unique objects for searching microorganisms and studying ancient ecological events that occurred during formation of icy layers. Complex microbiological and glaciological investigations at Vostok station carried out during a number of years resulted in the discovery of well-preserved cells of microorganisms of different taxonomic groups, as well as plant pollen and unicellular algae in the ice sheet horizons the age of which exceeds 300,000 years. Upon incubation of some samples with radiocarbon labeled organics an evidence of the preservation of some viable microorganisms has been provided. The investigation of ice bodies in an attempt to find any possible form of microscopical life has an advantage over analogous studies of other cosmic solids because the cells of microorganisms and other inclusions can be released from the melted ice without destruction and can be studied unambiguously by different methods of microscopy.

Antarctic ice sheet as a model in search of life on other planets

Abstract This paper concerns the problem of search of life on other planets due to similarities of some conditions in polar ice caps of Earth and Mars. Viable microbes were isolated from layers of the Antarctic ice sheet that dates back about 200 000 years. Their morphological variability and gradual restoration of some physiological functions in favourable conditions were described. The relation of microbes distribution at different horizons of ice to considerable fluctuations of Earths climate in ancient geological epochs was revealed. Those fluctuations of climate brought to the sharp variations of intensity of microparticles and microbes transfer with intercontinental aerial streams to polar caps of neighbouring planets.

Aging effects on translational lattice vibrations in ice Ih

Abstract Laser-Raman spectra of Vostok ice recovered from Antarctica have been measured in a frequency range of 10–400 cm −1 in order to observe long-term aging effects on Raman spectra of ice I h . We found that the intensity of the peak at 300 cm −1 increased as the depth of the ice core increased from 500 to 2452 m. Since no change in the peak height was observed by pressurization, the increase of the peak intensity is attributed to the aging effect on a structural change of ice during a very long period from 28 000 to 209 000 yr. Since this peak is assigned to a translational lattice vibration traveling along the hydrogen bonds, we conclude that the proton arrangement in the Antarctic ice varies with a very long term aging.

Technology of nondestructive light gas extraction from ice tested on samples from a bore hole above Vostok Lake

Nondestructive technology has been developed for the extraction of light gases dissolved in ice. The technology has been tested on samples of atmospheric and congealed ice of the 5-G3 bore hole of the Vostok station (East Antarctica) extracted from depths of 3457–3698 m. Down to 3539 m, ice is of an atmospheric origin, while ice deposited deeper is formed by natural water of Vostok Lake frozen on the glacier. Light gases were extracted into samplers (glass flasks) in the course of the 3-day degassing of samples freshly elevated from a bore hole. The samples were analyzed on the FT-1 time-of-flight mass spectrometer 6 months after sampling. Measurements reveal the presence of amounts of helium as well as molecular hydrogen considerably exceeding the atmospheric values. Measured values of gas ratio H2/4He = 5.4 ± 1.9 in the samples from depths of 3596–3698 m exceed the atmospheric values by more than an order of magnitude.

Content and Isotope Ratios of Noble Gases in Congelation Ice of Lake Vostok

Isotope ratios of noble gases (He, Ne, Ar) were studied in samples collected by degassing of cores of water frozen over a glacier of Lake Vostok. The gases were collected into glass retorts during three days of degassing of cores, which have just been extracted from the borehole. Within the error, the isotope 3He/4He ratios of 0.28 ± 0.08 RA (RA = 1.38 × 10–6 is the ratio for air) correspond to those from [1]. The 4He/20Ne and 40Ar/36Ar ratios (12.4 ± 4.6 RA and 1.0074 ± 0.0023 RA, respectively) exceed their contents in air (4He/20NeA = 0.29; 40Ar/36ArA = 298.6) and may indicate some contribution of terrigenous gas to the gaseous balance of the lake, as well as the high content of ancient ground waters in the lake. The 3He/4He ratio of 0.28 RA means low mantle 3He flux typical of continental platforms far from active rift zones.