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  • 1
    Electronic Resource
    Electronic Resource
    The Origin Of Continents (1966)
    [s.l.] : Nature Publishing Group
    Nature 210 (1966), S. 669-670 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE origin of continental nuclei has long been a puzzle. Theories advanced so far have generally failed to explain the first step in continent growth, or have been subject to serious objections. It is the purpose of this article to examine the possible role of the impact of large meteorites or ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/210669a0
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  • 2
    Electronic Resource
    Electronic Resource
    Surface Density of Large Lunar Craters (1968)
    [s.l.] : Nature Publishing Group
    Nature 218 (1968), S. 1147-1149 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1. Contour map of the number per block o craters larger than 10 km in diameter. The contour values indicate the ratio of the density of craters to the total number of craters times 10*. The terra-mare dichotomy and the "nesting" in the terrae are clearly visible. Total number of craters ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2181147a0
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  • 3
    Electronic Resource
    Electronic Resource
    The shape of asteroids: Theoretical considerations (1979)
    Springer
    Earth, moon and planets 21 (1979), S. 409-417 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Theoretical consideration and observations by other authors indicate that small asteroids are capable of maintaining irregular shapes, notably the shape of a cigar and even of a dumb-bell. This paper presents a model which describes the changes in the shape of an asteroid due to collisions of smaller objects (meteoroids) with the asteroid. The following assumptions must be approximately valid: (1) collisions are not uncommon; (2) collisions between a (relatively) large asteroid and small objects (meteroids) are more common than collisions between asteroids; (3) the cumulative probability of the collision of a meteoroid on a point on the surface of an asteroid is proportional to the zenith angle of the horizon as seen by that point; (4) obliquities of all but the major asteroids are random, so that there is not a preferred side on which collisions occur; (5) a considerable percentage of collision ejecta achieves escape velocity; and (6) the rate of erosion of each point on the surface of an asteroid is proportional to the cumulative probability of collision. Generalized conclusions that are obtained from the computer running of the model indicate that both cigars and dumb-bells are possible outcomes. Sharp corners are smoothed away, the radius of curvature of rounded surfaces increases to the point of going from convexity to concavity, and flat surfaces develop into gentle concavities. Collisions of an asteroid with an object of sufficient size such that the impact causes the breakage of the asteroid or the formation of a large crater, are not discussed in this paper. Previous work, however, suggests that the crater will undergo geomorphological changes of different geometry than a similar crater on the Moon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00897834
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  • 4
    Electronic Resource
    Electronic Resource
    Aeolian regime of the surface of Venus (1970)
    Springer
    Astrophysics and space science 8 (1970), S. 59-65 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent probes of the planet Venus reveal a probable surface temperature exceeding 700K and a pressure exceeding 100 atm. A very dusty lower atmosphere may exist which is composed of micron-sized particles kept airborne by mild turbulence and a gentle circulation of deep adiabatic currents. A study of surface conditions responsible for generation and persistence of surface dust clouds is of fundamental importance in the radiative and dynamic properties of the atmosphere. Also spurious radar echoes may be caused by suspended particulate matter, thus explaining the high relief reported by radar altimeters. Equations describing transportation and deposition of dust and sand have been solved for the surface conditions of Venus. It is concluded that the minimum wind velocity for initiating grain movement is about one order of magnitude smaller than on Earth. In addition, this minimum wind velocity occurs for smaller particles on Venus than on Earth. Once the particles are raised, they can be maintained aloft for longer periods of time and over a larger size range on Venus. Surface structures such as ripples evolved from aeolian deposition are likely to be of smaller vertical dimensions but larger horizontally when compared with equivalent structures on Earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00651655
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  • 5
    Electronic Resource
    Electronic Resource
    Maxwell Montes and Thessera Fortuna: A study of Venera 15 and 16 radar images (1986)
    Springer
    Earth, moon and planets 36 (1986), S. 23-39 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The radar images of Maxwell Montes and Thessera Fortuna obtained by Venera 15 and 16 were analyzed. It was concluded that the structures are not aeolian but are tectonic deformations. Because of the lack of large-scale erosion, these deformations must have been formed near the surface and, therefore, one of the principal stress axes must have been vertical. The orientations of the stress ellipsoid in several localities are presented. Differences between localities in the types of deformation can be explained by changes in the orientation of the intermediate stress axis, while the major stress axis remains constant. The latter is generally horizontal and oriented EW. Other differences may be caused by a shift from a compressional to an extensional regime. Inhomogeneities in the stress field have caused shear zones. Block diagrams are developed to explain the postulated structures. The described features are not unique to the studied areas; thus the method used and the conclusions reached have planetary implications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00113882
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  • 6
    Electronic Resource
    Electronic Resource
    Topographic changes on airless bodies: Theoretical considerations (1977)
    Springer
    Earth, moon and planets 17 (1977), S. 233-257 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A theoretical model of the evolution of topographic features on airless bodies is based on the erosion caused by the impact of small meteorites and the deposition of material ejected from nearby impacts. Three differing conditions are postulated: (i) the rate of erosion equals the rate of sedimentation, as may be expected on large bodies like the Earth's moon and Mercury, (ii) the rate of erosion exceeds the rate of sedimentation, as may be expected in smaller bodies like the asteroids, where portions of the ejecta may reach escape velocity, and (iii) the rate of sedimentation exceeds the rate of erosion, as may be expected on bodies during planetary growth. Although quantitative conclusions cannot yet be reached, qualitative relationships appear to exist, capable of elucidating the mass balance of airless planetary bodies. Under conditions of erosion equalling sedimentation, a crater tends to evolve into a rim-less bowl, the center of which is below the level of the surrounding plain. Under conditions of high erosion, the tendency for a crater is to evolve into a circular low hill around a bowl, the center of which is at the same level as the surrounding plain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562198
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  • 7
    Electronic Resource
    Electronic Resource
    A possible lunar outcrop: a study of lunokhod-2 data (1977)
    Springer
    Earth, moon and planets 17 (1977), S. 19-28 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The remotely controlled vehicle Lunokhod-2 travelled extensively around the edges of a linear depression unofficially called Fossa Recta. The edges of the Fossa are marked by elongated boulder fields. Three lines of reasoning suggest that the boulder fields are not the usual ‘erratic’ boulders found on a normal mare surface, but are bedrock protuberances: (1) The morphology of many boulders is reminiscent of primary lava features, (2) toward the edge of the Fossa the regolith thins out; (3) a model of lunar ‘gardening’ indicates that no regolith is to be expected in the upper portion of a non-impact cliff.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566850
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  • 8
    Electronic Resource
    Electronic Resource
    Lunar craters evolution and meteoroidal flux in pre-mare and post-mare times (1981)
    Springer
    Earth, moon and planets 24 (1981), S. 209-229 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In order to study the geomorphic evolution and lifetimes of lunar craters, data were collected from (i) 32mare andterra provinces of the nearside of the Moon using the L.P.L. catalog; (ii) amare area in Sinus Medii, using direct observations of Lunar Orbiter photos, and (iii) aterra area on the farside using direct observations of Zond-8 photos. The theory presented in a previous publication is expanded and applied to the data. The following conclusions are obtained. (1) Steady-state conditions occur on the studiedmare surfaces for craters of diameter up to approximately 220 m, and on the studiedterra surfaces for craters of diameter up to at least 50 km. (2) The average lifetime of a crater, in addition of being a function of the meteoroidal flux, is a steep function of the diameter of the crater. (3) The correlation is good between a geomorphic classification of craters based on visual comparison with standard craters and a classification of craters based on their depth-diameter ratio, resulting in a coefficient of rank correlation of 0.64. (4) When craters are classified as young, mature, and old, the length of time spent as young is less than a few percent of the total lifetime of the crater; the time spent as mature is 10 to 30%; and as much as 80% is spent as an old crater. Within the error of the calculations, these values are independent of crater diameter and apply to both pre-mare and post-mare craters, indicating that they are also independent of the intensity of the meteoroidal flux. (5) The average lifetime of a 50 km crater in pre-mare times is estimated to be less than 0.3×109 years. (6) The average lifetime of a 50 km crater in post-mare times is estimated to be between 3×1011 and 1014 years. (7) The average meteoroidal flux in pre-mare times is estimated to be three to six orders of magnitude more intense than in post-mare times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00910609
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  • 9
    Electronic Resource
    Electronic Resource
    On the rate of ancient meteoroidal flux: Studies of the pre-mare crater population on the Moon (1980)
    Springer
    Earth, moon and planets 23 (1980), S. 355-371 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract According to radiometric dating of lunar rocks, meteoroidal bombardment and accompanying cratering on the Moon were intensive in the first 0.7×109 y, the so-calledterra stage. Recently the hypothesis of a ‘terminal cataclysm’ has been gaining acceptance, meaning that a sharp increase in the bombardment followed by a steep decay occurred at the end of theterra stage. The purpose of this paper is to investigate possible variations in the intensity of the bombardment during theterra stage by analyzing the population of large (3–1000 km)terra craters and comparing it with results obtained by theoretical models. The proportion of fresh craters is specifically used. Observational data were obtained by studying the craters on an oldterra surface photographed by Zond 8 and/or covered by LTO and LM maps and by conducting a statistical study of theterra listed in the Lunar and Planetary Laboratory Catalog. Mathematical models were developed in such a way as to make them dimensionless, and as such applicable even without the knowledge of the physical constants and variables involved. Particularly powerful is the method of measuring time as multiples of the average lifetime of a crater of that size. The following conclusions and/or interpretations are reached. (1) A crater remains ‘fresh’ for less than 20% of the average life of a crater of that size. (2) A condition of equilibrium (i.e., on the average, a new impact does not cause a net increase in the total number of craters) is reached or almost reached on lunarterrae. (3) The age of theterra surface is more than three average lifetimes of the 2 km to at least 20 km size craters (4) The observedterra crater population isnot the result of two cataclysms, one at the beginning of the stage and one at the end. (5) This population, however, could be the result of a constant or slowly decaying flux continuing until the end of the stage, when the terminal cataclysms occurred. This sequence of events cannot be proven or disproven. (6) If no terminal cataclysm occurred, then the meteoroidal flux during theterra stage was slowly decaying or constant. (7) The formation of all the large multi-ringed basins essentially contemporaneously is doubtful.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00902050
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  • 10
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    Unknown
    The Ages of the Lunar Seas (1971)
    National Academy of Sciences
    Details
    Publication Date: 1971-06-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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