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  • 1
    Electronic Resource
    Electronic Resource
    The cryptoendolithic microbial environment in the Ross Desert of Antarctica: Satellite-transmitted continuous nanoclimate data, 1984 to 1986 (1987)
    Springer
    Polar biology 7 (1987), S. 273-287 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A satellite mediated station for monitoring nanoclimate (climate in the millimeter range) data, suitable for use in polar regions is described. The station, located in the Ross desert of Antarctica, has been in operation for more than 3 years, measuring rock temperatures, air temperature, light, snow, wind, and moisture. The data indicate that biological activity in the cryptoendolithic microbial ecosystem is limited to the period from mid November to mid February. The total number of hours of biological activity, based on assumptions of the minimum light, temperature and moisture requirements of the community, is less than 1000 h/year. The time above 0°C, representing more nearly optimal conditions, is between 50 and 550 h/year, depending on the orientation of the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00443945
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  • 2
    Electronic Resource
    Electronic Resource
    Paleolakes on Mars (1995)
    Springer
    Journal of paleolimnology 13 (1995), S. 267-283 
    Details
    ISSN: 1573-0417
    Keywords: Mars ; martian paleolakes ; lacustrine sediments ; ice-covered lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Observational evidence such as outflow channels and valley networks suggest that in the past there was flowing water on Mars. The images of fluvial features on Mars logically suggest that there must exist downstream locations in which the water pooled and the sediment load deposited (i.e. lakes). Sediments and morphological features associated with the martian paleolakes are believed to occur in Valles Marineris, and several large basins including Amazonis, Chryse and Elysium planitia. As Mars became progressively colder over geological time, any lakes on its surface would have become seasonally, and eventually perennially ice-covered. We know from polar lakes on Earth that ice-covered lakes can persist even when the mean annual temperature falls below freezing. Thus, the most recent lacustrine sediments on Mars were probably deposited in ice-covered lakes. While life outside of the Earth's atmosphere has yet to be observed, there is a general consensus among exobiologists that the search for extraterrestrial life should be based upon liquid water. The inference that there was liquid water on Mars during an earlier epoch is the primary motivation for considering the possibility of life during this time. It would be of enormous interest from both an exobiological and paleolimnological perspective to discover lakes or the evidence of former lakes on another planet such as Mars. Limnology would then become an interplanetary science.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682769
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  • 3
    Electronic Resource
    Electronic Resource
    Origins of life: A comparison of theories and application to Mars (1996)
    Springer
    Origins of life and evolution of the biospheres 26 (1996), S. 61-73 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The field of study that deals with the origins of life does not have a consensus for a theory of life's origin. An analysis of the range of theories offered shows that they share some common features that may be reliable predictors when considering the possible origins of life on another planet. The fundamental datum dealing with the origins of life is that life appeared early in the history of the Earth, probably before 3.5 Ga and possibly before 3.8 Ga. What might be called the standard theory (the Oparin-Haldane theory) posits the production of organic molecules on the early Earth followed by chemical reactions that produced increased organic complexity leading eventually to organic life capable of reproduction, mutation, and selection using organic material as nutrients. A distinct class of other theories (panspermia theories) suggests that life was carried to Earth from elsewhere — these theories receive some support from recent work on planetary impact processes. Other alternatives to the standard model suggest that life arose as an inorganic (clay) form and/or that the initial energy source was not organic material but chemical energy or sunlight. We find that the entire range of current theories suggests that liquid water is the quintessential environmental criterion for both the origin and sustenance of life. It is therefore of interest that during the time that life appeared on Earth we have evidence for liquid water present on the surface of Mars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01808160
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  • 4
    Electronic Resource
    Electronic Resource
    Life on Mars (1996)
    Springer
    Origins of life and evolution of the biospheres 26 (1996), S. 300-300 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459770
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  • 5
    Electronic Resource
    Electronic Resource
    The cryptoendolithic microbial environment in the Antarctic cold desert: Temperature variations in nature (1985)
    Springer
    Polar biology 4 (1985), S. 19-25 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the Antarctic cold desert, cryptoendolithic microorganisms live under the surface of porous sandstone rocks. During the austral summer, the environment of the near-surface rock layers colonized by organisms is characterized by two kinds of temperature oscillations, both occurring across the freezing point. Low-frequency (diurnal) and large-amplitude (up to about 20°C) oscillations on the sunlit surface of rocks result in a daily freeze-thaw cycle. This is a result of the diurnal changes in the sun altitude and angle with respect to the rock surface. The biological effect of this oscillation is the regulation of the onset and cessation of metabolic activity. The high-frequency (few minutes) oscillations occur only under certain weather conditions (sunny days with light winds) and are superimposed on the low-frequency oscillations. They are caused by the cooling effect of wind gusts on rock surfaces that are much warmer than ambient air temperatures. High-frequency oscillations result in a rapid freeze-thaw cycle on the surface, which, however, does not reach the microbial zone. These high-frequency freeze-thaw oscillations are probably the cause of the abiotic nature of the rock surface. Both oscillations seem to have an effect on rock weathering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00286813
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  • 6
    Electronic Resource
    Electronic Resource
    The cryptoendolithic microbial environment in the Ross Desert of Antarctica: Light in the photosynthetically active region (1988)
    Springer
    Microbial ecology 16 (1988), S. 271-289 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The vertical zonation of the Antarctic cryptoendolithic community appears to form in response to the light regime in the habitat. However, because of the structure of the habitat, the light regime is difficult to study directly. Therefore, a mathematical model of the light regime was constructed, which was used to estimate the total photon flux in different zones of the community. Maximum fluxes range from about 150μm photons m−2 s−1 at the upper boundary of the community to about 0.1μm photons m−2 s−1. Estimates of the annual productivity in the community indicate that the lowest zone of the community is light limited, with the maximal annual carbon uptake equivalent to less than the carbon content of one algal (Hemichloris) cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02011700
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  • 7
    Electronic Resource
    Electronic Resource
    The cryptoendolithic microbial environment in the Ross Desert of Antarctica: Mathematical models of the thermal regime (1988)
    Springer
    Microbial ecology 16 (1988), S. 253-270 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microbial activity in the Antarctic cryptoendolithic habitat is regulated primarily by temperature. Previous field studies have provided some information on the thermal regime in this habitat, but this type of information is limited by the remoteness of the site and the harsh climatic conditions. Therefore, a mathematical model of the endolithic thermal regime was constructed to augment the field data. This model enabled the parameters affecting the horizontal and altitudinal distribution of the community to be examined. The model predicts that colonization should be possible on surfaces with zenith angle less than 15°. At greater zenith angles, colonization should be restricted to surfaces with azimuth angles less than 135° or greater than 225°. The upper elevational limit of the community should be less than 2,500 m. The thermal regime probably does not influence the zonation of the community within a rock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02011699
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  • 8
    Electronic Resource
    Electronic Resource
    Perennially ice-covered Lake Hoare, Antarctica: physical environment, biology and sedimentation (1989)
    Springer
    Hydrobiologia 172 (1989), S. 305-320 
    Details
    ISSN: 1573-5117
    Keywords: Antarctica ; climatic changes ; gas solubility ; ice-covered lakes ; Lake Hoare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Hoare (77° 38′ S, 162° 53′ E) is a perennially ice-covered lake at the eastern end of Taylor Valley in southern Victoria Land, Antarctica. The environment of this lake is controlled by the relatively thick ice cover (3–5 m) which eliminates wind generated currents, restricts gas exchange and sediment deposition, and reduces light penetration. The ice cover is in turn largely controlled by the extreme seasonality of Antarctica and local climate. Lake Hoare and other dry valley lakes may be sensitive indicators of short term (〈 100 yr) climatic and/or anthropogenic changes in the dry valleys since the onset of intensive exploration over 30 years ago. The time constants for turnover of the water column and lake ice are 50 and 10 years, respectively. The turnover time for atmospheric gases in the lake is 30–60 years. Therefore, the lake environment responds to changes on a 10–100 year timescale. Because the ice cover has a controlling influence on the lake (e.g. light penetration, gas content of water, and sediment deposition), it is probable that small changes in ice ablation, sediment loading on the ice cover, or glacial meltwater (or groundwater) inflow will affect ice cover dynamics and will have a major impact on the lake environment and biota.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00031629
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  • 9
    Electronic Resource
    Electronic Resource
    The evolution of nitrogen cycling (1988)
    Springer
    Origins of life and evolution of the biospheres 18 (1988), S. 311-325 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Based upon arguments concerning properties of the environment and the energetics of nitrogen transformation reactions, new hypotheses regarding their evolution are presented. These hypotheses are supported by new calculations and observations germane to understanding the evolution of the nitrogen cycle. From calculations of shock production by meteor impact, we suggest that impact produced fixed nitrogen could have resulted in the entire reservoir of Earth's N2 being converted into fixed nitrogen at the end of accretion. We have significantly improved upon previous calculations of the abiotic fixation rate on the early earth and find a rate of fixation by lightning of ∼1−3 × 1016 Molecules NO/J, which is 2 to 3 times greater than previous estimates. This strengthens the suggestion, corroborated by the predominance of a single nitrogenase enzyme, that biological nitrogen fixation may have been a late evolutionary development, after the development of an aerobic atmosphere. In addition, we show for the first time that HNO, predicted to be the main product of atmospheric photochemical reactions involving NO on the primitive Earth by photochemical models, would eventually become NO2 − and NO3 − after reaching the Earth's surface. Based upon microbe-environment interactions on an ecological as well as a biochemical scale we suggest that denitrification arose prior to aerobic respiration and that nitrification arose after the advent of an aerobic atmosphere. We hypothesize the following evolutionary sequence for the biological transformation of nitrogen compounds: Ammonification → Denitrification → Nitrification → Nitrogen fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01808213
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  • 10
    Electronic Resource
    Electronic Resource
    Origins of life: A comparison of theories and analogy to mars (1996)
    Springer
    Origins of life and evolution of the biospheres 26 (1996), S. 509-509 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459899
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