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Biological Contamination of Mars Issues and Recommendations (1992) / Chapter Skim
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3 SURFACE ENVIRONMENT OF MARS
Pages 23-29

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From page 23...
... The Viking lander inorganic experiment detected most major elements heavier than magnesium and a number of minor elements. Several chemical species of biologic significance (C, N, H2O, P)
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From page 24...
... The isotopic ratios of nitrogen, argon, and xenon are identical, within analytical error, to the ratios found in the martian atmosphere, as determined by Viking, and are distinctively different from those of any other known source in the solar system, including Earth. The SNC meteorites contain a variety of secondary minerals such as illite and smectite clays and water-precipitated salts such as calcium and magnesium carbonate, calcium sulfate, magnesium phosphate, and hematite (Table 3.1)
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From page 25...
... Doses from secondary radiation also accrue within the upper 50 centimeters of the regolith. At low elevations, where the atmosphere provides maximum protection, the OCR doses approach annual limits allowed for humans but fall far short of values commonly certified for sterilization of food.
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From page 26...
... Any summer increase in ground temperature is restricted to shallower depths. WATER Estimates of the amount of water present at the martian surface have ranged widely in recent years.10-13 However, recent recognition of the efficacy of gas-dynamic escape and impact erosion in removing volatiles from the planet early in its history has undermined geochemical arguments for low water abundances and has led to greater credence of the higher geologic estimates based on the observed effects of water on the surface.
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From page 27...
... At low latitudes, where mean annual temperatures exceed 200 K, the ground is generally expected to be ice-free to depths of a few hundred meters. However, anomalous combinations of albedo, thermal inertia, and porosity could result in nearsurface ice locally.
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From page 28...
... However, terrains that date from the early period are highly degraded and commonly dissected by branching valley networks.14,11 The networks resemble dry terrestrial river valleys and are thought to have been formed by slow erosion owing to running water. Despite uncertainty about the precise conditions required for these valleys to form, it is probable that some combination of high heat flow and high surface temperatures is required.
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From page 29...
... 1991. "Ancient Oceans, Ice Sheets and the Hydrological Cycle on Mars." Nature 351:589-594.
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Key Terms

  • snc meteorites
  • surface environment
  • mean annual
  • volcanic activity
  • low latitudes

  • volcanically active
  • surface temperatures
  • near surface
  • annual temperatures
  • martian origin

  • viking sites
  • viking lander
  • thermal inertia
  • water absorbed
  • ionizing radiation

  • thin atmosphere
  • secondary minerals
  • remain close
  • short period
  • hydrothermal activity

  • volcanic ash
  • ocr protons
  • temperatures remain
  • recent recognition
  • surface unless

  • water abundances
  • meteorites contain
  • surface temperature
  • entire martian
  • ground ice


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