The microwave spectrum of Mercury
Mercury disk temperature from microwave spectrum analysis, proposing subsurface greenhouse effect
Klein, M. J.↗
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The long winter model of Martian biology: A speculation
An estimated mean thickness of about 1 km of frost in the Martian north polar cap summer remnant, if vaporized, would yield about 1000 g/sq cm of atmosphere over the planet, higher global temperatures through the greenhouse effect, and a greatly increased likelihood of liquid water. Vaporization of such cap remnants may occur twice each equinoctial precession, and Martian organisms may now be in cryptobiotic repose awaiting the end of the long precessional winter. The Viking biology experiments can test this hypothesis.
Sagan, C.↗
The long winter model of Martian biology - A speculation.
A temporal microenvironment model is proposed for Martian biology that is based on an estimated mean thickness of nearly 1 km of frost in the Martian north polar cap summer remnant. If vaporized, this frost could yield not only 1 kg per sq cm of atmosphere, but also higher global temperatures through the greenhouse effect and a greatly increased likelihood of liquid water. Vaporization of such cap remnants may occur twice each equinoctial precession, and Martian organisms may now be in cryptobiotic repose awaiting the end of the long precessional winter. The Viking biology experiments might test this hypothesis.
Sagan, C.↗
The greenhouse of Titan.
Analysis of non-gray radiative equilibrium and gray convective equilibrium on Titan suggests that a massive molecular-hydrogen greenhouse effect may be responsible for the disagreement between the observed IR temperatures and the equilibrium temperature of an atmosphereless Titan. Calculations of convection indicate a probable minimum optical depth of 14 which corresponds to a molecular hydrogen shell of substantial thickness with total pressures of about 0.1 bar. It is suggested that there is an equilibrium between outgassing and blow-off on the one hand and accretion from the protons trapped in a hypothetical Saturnian magnetic field on the other, in the present atmosphere of Titan. It is believed that an outgassing equivalent to the volatilization of a few kilometers of subsurface ice is required to maintain the present blow-off rate without compensation for all geological time. The presence of an extensive hydrogen corona around Titan is postulated, with surface temperatures up to 200 K.
Sagan, C.↗
Infrared photometry and spectrophotometry of Titan
The wide variation in infrared brightness temperature of Titan is explained in terms of a greenhouse effect. Radiometric observations in the infrared and microwave frequencies indicate an alternate hot atmospheric model. Methane, ammonia, hydrogen atoms, and nitrogen atoms are suggested as main constituents for the Titan atmosphere.
Morrison, D.↗
Comparative evaluation of solar, fission, fusion, and fossil energy resources. Part 5: Conclusions and recomendations
Air pollution resulting from the use of fossil fuels is discussed. Phenomena relating to the emission of CO2 such as the greenhouse effect and multiplier effect are explored. Particulate release is also discussed. The following recommendations are made for the elimination of fossil fuel combustion products in the United States: development of nuclear breeder reactors, use of solar energy systems, exploration of energy alternatives such as geothermal and fusion, and the substitution of coal for gas and oil use.
Williams, J. R.↗
Atmosphere of Venus: Implications of Venera 8 sunlight measurements
Venera 8 measurements of solar illumination within the atmosphere of Venus are quantitatively analyzed by using a multilayer model atmosphere. The analysis shows that there are at least three different scattering layers in the atmosphere of Venus and the total cloud optical thickness is about 10 or greater. However, because of the nature of the observations, it is not possible to determine the vertical distribution of absorbed solar energy, which would reveal the drive for the atmospheric dynamics and the strength of the greenhouse effect. Future spacecraft observations should be designed to (1) measure both upward and downward solar fluxes, (2) include measurements of the highest cloud layers, and (3) employ narrow-band and broad-band sensors.-
Lacis, A. A.↗
The atmosphere of Titan
Titan, a satellite of Saturn, is unique in that it is the only satellite in the solar system with an extensive atmosphere, possibly more massive than that of the earth. Methane and hydrogen have been discovered, and a greenhouse effect is apparent from infrared measurements. It may be enshrouded by clouds, and this intriguing body may, in time, provide clues to the evolution of the major planets and their satellites. At present, interpretation of the observational evidence concerning the properties of Titan is somewhat speculative and controversial. The status of the observations and theoretical studies is assessed.
Gross, S. H.↗
The structure and circulation of the deep Venus atmosphere
A simple model for the structure of a nonrotating Hadley regime in an atmosphere with large thermal inertia is developed. The radiative fluxes are estimated by using a linearization about the radiative equilibrium state, and the dynamical fluxes are estimated by using scaling analysis. The requirement that differential heating by these fluxes be in balance in both the meridional and vertical directions leads to two equations for the mean static stability and meridional temperature contrast. The solution depends on two parameters: the strength of the radiative heating, as measured by the static stability of the radiative equilibrium state; and the ratio of the time it takes an external gravity wave to traverse the atmosphere to the time it would take the atmosphere to cool off radiatively. It is shown that it is not necessary to invoke convection to explain the approximate adiabatic lapse rate in the Venus atmosphere, but a greenhouse effect is necessary to explain the high surface temperatures.
Stone, P. H.↗
Consideration of probability of bacterial growth for Jovian planets and their satellites
Environmental parameters affecting growth of bacteria are compared with current atmospheric models for Jupiter and Saturn, and with the available physical data for their satellites. Different zones of relative probability of growth are identified for Jupiter and Saturn. Of the more than two dozen satellites, only the largest (Io, Europa, Ganymede, Callisto, and Titan) are found to be interesting biologically. Titan's atmosphere may produce a substantial greenhouse effect providing increased surface temperatures. Models predicting a dense atmosphere are compatible with microbial growth for a range of pressures at Titan's surface. For Titan's surface the probability of growth would be enhanced if: (1) the surface is entirely or partially liquid; (2) volcanism is present; or (3) access to internal heat sources is significant.
Taylor, D. M.↗
Calculations of the radiative and dynamical state of the Venus atmosphere
Results are reported for accurate multiple-scattering calculations to determine the solar-energy deposition profile in the atmosphere of Venus. It is found that most of the absorbed energy is deposited in the main cloud-layer region, located at altitudes above 35 km, and that the ground receives approximately 3% of the energy absorbed in toto by Venus. Using these results, vertical temperature profiles are computed under conditions of pure radiative equilibrium and radiative-convective equilibrium. Since the latter results satisfactorily match the temperature structure determined from various spacecraft observations, it is inferred that the greenhouse effect can account for the high surface temperature. Aerosols make an important contribution to the infrared opacity in these calculations. Preliminary three-dimensional calculations of the general circulation of the atmosphere are discussed which incorporate the results of the radiative calculations.
Pollack, J. B.↗
Microwave boundary conditions on the atmosphere and clouds of Venus
The dielectric properties of H2O/H2SO4 mixtures are deduced from the Debye equations and, for a well-mixed atmosphere, the structure of H2O and H2O/H2SO4 clouds is calculated. Various data on the planet together set an upper limit on the mixing ratio by number for H2O of about 0.001 in the lower Venus atmosphere, and for H2SO4 of about 0.00001. The polarization value of the real part of the refractive index of the clouds, the spectroscopic limits on the abundance of water vapor above the clouds, and the microwave data together set corresponding upper limits on H2O of approximately 0.0002 and on H2SO4 of approximately 0.000009. Upper limits on the surface density of total cloud constituents and of cloud liquid water are, respectively, about 0.1 g/sq cm and about 0.01 g/sq cm. The infrared opacities of 90 bars of CO2, together with the derived upper limits to the amounts of water vapor and liquid H2O/H2SO4, may be sufficient to explain the high surface temperatures through the greenhouse effect.
Rossow, W. B.↗
Consideration of probability of bacterial growth for Jovian planets and their satellites
Environmental parameters affecting growth of bacteria (e.g., moisture, temperature, pH, and chemical composition) were compared with current atmospheric models for Jupiter and Saturn, and with the available physical data for their satellites. Different zones of relative probability of growth were identified for Jupiter and Saturn, with the highest in pressure regions of 1-10 million N/sq m (10 to 100 atmospheres) and 3-30 million N/sq m (30 to 300 atmospheres), respectively. Of the more than two dozen satellites, only the largest (Io, Europa, Ganymede, Callisto, and Titan) were found to be interesting biologically. Titan's atmosphere may produce a substantial greenhouse effect providing increased surface temperatures. Models predicting a dense atmosphere are compatible with microbial growth for a range of pressures at Titan's surface. For Titan's surface the probability of growth would be enhanced if (1) the surface is entirely or partially liquid (water), (2) volcanism (in an ice-water-steam system) is present, or (3) access to internal heat sources is significant.
Taylor, D. M.↗
Can internal heat contribute to the high surface temperature of Venus
It is shown that current observational data on conditions at the Venusian surface are adequate to exclude the possibility that thermal energy from a hot interior contributes to the high surface temperature of the planet. The maximum energy flux conducted from the interior is estimated by assigning a maximum thermal conductivity and a minimum thickness to the crust. It is found that the crust must be at least 10 km thick and that the maximum thermal flux for this thickness is about 6 millionths of a calorie per sq cm/sec. The relative importance of this internal energy source is assessed by comparing it with the amount of solar energy deposited at the surface. The result demonstrates that the absorbed solar energy is at least one and probably two orders of magnitude higher than the minimum flux conducted from the interior. It is concluded that a very efficient atmospheric trapping mechanism (the greenhouse effect) is operating on Venus.
Morrison, D.↗
Reducing greenhouses and the temperature history of earth and Mars
It has been suggested that NH3 and other reducing gases were present in the earth's primitive atmosphere, enhancing the global greenhouse effect; data obtained through isotopic archeothermometry support this hypothesis. Computations have been applied to the evolution of surface temperatures on Mars, considering various bolometric albedos and compositions. The results are of interest in the study of Martian sinuous channels which may have been created by aqueous fluvial errosion, and imply that clement conditions may have previously occurred on Mars, and may occur in the future.
Sagan, C.↗
Planets of the solar system
Venera and Mariner spacecraft and ground based radio astronomy and spectroscopic observations of the atmosphere and surface of venus are examined. The composition and structural parameters of the atmosphere are discussed as the basis for development of models and theories of the vertical structure of the atmosphere, the greenhouse effect, atmospheric circulation and cloud cover. Recommendations for further meteorological studies are given. Ground based and Pioneer satellite observation data on Jupiter are explored as well as calculations and models of the cloud structure, atmospheric circulation and thermal emission field of Jupiter.
Kondratyev, K. Y.↗
Scale covariant cosmology and the temperature of the earth
Geological data are used as cosmological determinants in a study of the temperature of the early earth (2.3 to 4.5 billion years ago). It is known that the energy output of the sun during that period was on the order of 30-40% lower than at present, and deduced that the mean temperature of the earth should have fallen to as low as 245 K, i.e., below the freezing point of seawater. Strong evidence exists, however, to indicate that algae (therefore liquid water) was present. To reconcile the discrepancies, a model is proposed whereby terrestrial G and M vary. It is further noted that atmosphere H2 may be a better agent than NH3 for producing a greenhouse effect.
Canuto, V.↗
Primitive atmosphere and implications for the formation of channels on Mars
It is suggested that, if primitive Mars had a reducing atmosphere composed mainly of methane, this atmosphere could be polymerized by solar ultraviolet radiation to produce higher hydrocarbons. These compounds, which would be low-viscosity liquids at present temperatures on Mars, could have contributed to the formation of channels. The Martian atmosphere model used in the analysis is similar to Sagan's (1977), except that ammonia is omitted. Major reactions in this early Martian atmosphere are examined, and the number densities of the lighter alkanes in the lower atmosphere of Mars are determined. Since the photochemical mechanism investigated here would provide only a modest amount of fluid for a comparatively brief period of time (10-100 million years), liquid alkanes would not be the major factor in the formation of the channels, although their derivatives could contribute to the greenhouse effect or depress the freezing point of water.
Yung, Y. L.↗