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  • 1985-1989  (9)
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  • 1
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    Absorption of the Martian regolith: Specific surface area and missing CO(sub 2) (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: For most estimates of available regolith and initial degassed CO(sub 2) inventories, it appears that any initial inventory must have been lost to space or incorporated into carbonates. Most estimates of the total available degassed CO(sub 2) inventory are only marginally sufficient to allow for a major early greenhouse effect. It is suggested that the requirements for greenhouse warming to produce old dessicated terrain would be greatly lessened if groundwater brines rather than rainfall were involved and if a higher internal gradient were involved to raise the water (brine) table, leading to more frequent sapping.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., MECA Symposium on Mars: Evolution of its Climate and Atmosphere; p 123-125
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  • 2
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    Episodic vs. epochal release of SO2 on Mars (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Erosion of the Martian surface by the flow of liquid water has apparently taken place at different times and locations on the planet. Many attempts were made to explain the valley networks by invoking a strong atmospheric CO2/H2O greenhouse early in the history of the planet. It was assumed that the large amounts of CO2 necessary to cause the greenhouse would have disappeared due to carbonate formation. Carbonates have yet to be positively identified. Volcanism has occurred throughout much of the history of Mars. Presumably gases such as SO2 were released along with CO2 and H2O. Estimates of amounts and rates with which SO2 were released into the Martian atmosphere, and how this would effect the global climate were made. Studies are continuing on the effects of SO2 and other volcanic gases on Martian climatic history.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., MEVTV Workshop on Nature and Composition of Surface Units on Mars; p 101-102
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  • 3
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    Atmospheric H2O and the search for Martian brines (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Abundant martian brines would have important implication for current theories of volatile migration on Mars, since, although the presence of metastable brines is quite plausible, any brine in the reasonably near-surface should be completely depleted on a timescale short in relation to the age of Mars. It is important to determine whether brines exist in the martian subsurface, for the current paradigm for understanding martian volatile regime requires substantial alteration if they are found to exist. It is determined, however, that the prospect for detection of a subsurface brine via atmospheric water vapor measurements is marginal. Four reasons are given for this conclusion.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., MECA Workshop on Atmospheric H2O Observations of Earth and Mars. Physical Processes, Measurements and Interpretations; p 87-90
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  • 4
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    Possible origin of some channels on Alba Patera, Mars (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Several alternative models were proposed for the origin and mode of formation of channels and valley networks on Martian volcanoes, notably Hecates Tholus, Ceraunius Tholus, and Alba Patera. Early interpretations of Mariner 9 and Viking images suggested that these features on Alba were lava channels, while those on Ceraunius Tholus were interpreted as fluvial or volcanic debris channels. Subsequent mapping of Tyrrehna Patera and Hecate Tholus has suggested that pyroclastic activity may have characterized eruptions on these volcanoes, and that at least for Hecates the channels were probably formed by fluvial erosion of unconsolidated ash deposits on the flanks of the volcano. As part of a continuing program to better understand the eruptive history of the young volcanic centers on Mars, numerous channels were identified on the flanks of Alba Patera that resemble the channels on Hecates. As a result, the possibility is being explored that some of the small channels on the flanks of Alba Patera may be fluvial in origin and potentail water sources and modes of formation are being explored.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington, Reports of Planetary Geology and Geophysics Program, 1986; p 303-304
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  • 5
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    The role of regolith adsorption in the transition from early to late Mars climate (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Researchers reexamined radiative transfer models of early Mars that were advanced to show the existance of a greenhouse effect. These models were reexamined with regard to the effect that regolith adsorption may have had. It is argued that while the precipitation of carbonates has probably been an important process during Mars history, the rates at which this process could have taken place under early Mars conditions would have dropped sharply once liquid water was fairly scarce. Furthermore, conditions under which liquid water was available may have involved efficient recycling of carbonate so that steady state conditions rather than irreversible CO2 removal prevailed. In contrast, the growth of regolith surface area demands corresponding and predictable CO2 removal from the atmosphere-cap system and is fully capable of terminating any enhanced temperature regime on early Mars in the absence of any other effects.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington, Reports of Planetary Geology and Geophysics Program, 1986; p 161-162
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  • 6
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    Mars: Long Term Changes in the State and Distribution of H2O (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: A model for H2O distribution and migration on Mars was formulated which takes into account: (1) thermal variations at all depths in the regolith due to variations in obliquity, eccentricity and the solar constant; (2) variations in atmospheric PH2O caused by corresponding changes in polar surface insolation; and (3) the finite kinetics of H2O migration in both the regolith and atmosphere. Results suggest that regolith H2O transport rates are more strongly influenced by polar-controlled atmospheric PH2O variations than variations in pore gas PH2O brought about by thermal variations at the buried ice interface. The configuration of the ice interface as a function of assumed soil parameter and time is derived. Withdrawal of ice proceeds to various depths at latitudes less than 50 deg and is accompanied by filling of regolith pores at latitudes greater than 50 deg and transfer of H2O to the polar cap. The transfer has a somewhat oscillatory character, but only less than 1g/sq cm is shifted into and out the regolith during each obliquity cycle. It is concluded that this process combined with periodic thermal cycles played a major role in development of the fretted terrain, deflationary features in general, patterned ground, the north polar cap and the layered terrain.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 337
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  • 7
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    Effect of the greenhouse gases (CO2, H2O, SO2) on Martian paleoclimate (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: There is general agreement that certain surface features on Mars are indicative of the presence of liquid water at various times in the geologic past. In particular, the valley networks are difficult to explain by a mechanism other than the flow of liquid water. It has been suggested in several studies that a thick CO2 atmosphere on Mars early in its history could have provided a greenhouse warming that would have allowed the flow of water either on the surface or just below the surface. However, this effect was examined with a detailed radiation model, and it was found that if reduced solar luminosity early in the history of the solar system is taken into account, even three bars of CO2 will not provide sufficient greeenhouse warming. The addition of water vapor and sulflur dioxide (both plausible gases that may have been emitted by Martian volcanoes) to the atmosphere also fail to warm the surface above 273 K for reduced solar luminosity conditions. The increase in temperature may be large enough, however, for the formation of these features by brines.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 91; D431-D43
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  • 8
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    Distribution and state of H2O in the high-latitude shallow subsurface of Mars (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The state and distribution of H2O molecules at high latitudes are evaluated numerically with emphasis on the effects of seasonal temperatures on the kinetics of H2O transport. The investigation is carried out with a thermal model for the regolith regions from the surface through the ice interface and an atmospheric model for the H2O vapor density at the surface as a function of latitude. Few differences are found in the state and distribution of H2O whether the regolith is composed of Montmorillonite or basalt. During an obliquity cycle, the average exchanged H2O mass is determined to be in the range 1-20 gr/sq cm over the planetary surface, with a total maximum exchanged volume of 1500 cu km of H2O. The exchanged mass would arise mainly from ground ice in the case of a basalt regolith and from adsorbed H2O with Montmorillonite. Finally, seasonal ice stabilization is expected to occur at latitudes above 40 deg when obliquities exceed 25 deg.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 67; 19-36
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  • 9
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    Global distribution and migration of subsurface ice on Mars (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: An analytical model is developed for the factors which changed the initial distribution and state of H2O, mainly trapped as subsurface ice, on Mars. A uniform initial ice distribution is assumed, and changes in ice layer thickness are calculated at discrete latitudes of Mars. The thermal/diffusive model used for the calculations accounts for variations in the solar luminosity, the planetary obliquity and eccentricity, with obliquity starting 3.5 Gyr ago, and insolation at various latitudes. Attention is given to variations in the albedo due to seasonal CO2 variations, in the regolith temperature, and in atmospheric pressure. Migration of H2O into and out of the regolith is a function of the H2O vapor temperature at the subsurface ice boundary and the annual average H2O at the base of the atmosphere. Projections of the ice thickness over 100 obliquity periods indicate that the intensity of the obliquity effects are latitudinally dependent. H2O atmospheric concentrations are projected to vary up to six orders of magnitude over an obliquity cycle.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 67; 1-18
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