scholarly journals SCALING RELATIONSHIP BETWEEN THE WAVELENGTH OF LONGITUDINAL RIDGES AND THE THICKNESS OF LONG RUNOUT LANDSLIDES ON THE MOON

2021 ◽  
Author(s):  
G. Magnarini ◽  
T. M. Mitchell ◽  
P. M. Grindrod ◽  
H. H. Schmitt ◽  
N. E. Petro
Keyword(s):  
The Moon ◽  
Long Runout ◽  
Scaling Relationship

Longitudinal Ridges in Long Runout Landslides: on the Applicability of High-Speed Granular Flow Mechanisms.

2021 ◽  
Author(s):  
Giulia Magnarini ◽  
Thomas Mitchell ◽  
Peter Grindrod ◽  
Liran Goren
Keyword(s):  
Granular Flow ◽  
High Speed ◽  
Tensile Deformation ◽  
Granular Flows ◽  
Friction Material ◽  
Fault Mechanics ◽  
The Moon ◽  
Mechanical Instability ◽  
Long Runout ◽  
Erosion Rates

<p>Long runout landslides are a particular type of mass-wasting phenomena that belongs to the category of surface processes associated with rapid strain rates. The reduction of friction that has to be invoked to explain their high velocities and exceptional travel distance over nearly horizontal surfaces has yet to find satisfactory explanation. Inspired by fault mechanics studies, thermally-activated mechanisms can explain the dynamic frictional strength loss during sliding along the initial failure surface and the early development of velocities higher than expected. However, as slides continue moving along nearly horizontal valley floors, the weakening mechanisms required to sustain their exceptional behaviour are less certain.</p><p>Long runout landslides are found ubiquitous in our solar system and the slow erosion rates that operate on extraterrestrial planetary bodies allow the preservation of their geomorphological record. The availability of the latest high-resolution imagery of the surface of Mars and the Moon allows to conduct detailed morphometric analysis not so granted on our planet. On the other hand, on Earth, the partial loss of the geomorphological record due to fast erosion rates is compensated by the accessibility of sites that enable us to conduct field work. In order to better understand the mechanisms responsible for the apparent friction weakening we use a comparative planetary geology approach, in the attempt to link the morphology and the internal structures of long runout landslide deposits to the mechanisms involved during the emplacement of such catastrophic events.</p><p>We focused on the distinctive longitudinal ridges that mark the surface of the landslide deposits. The formation mechanism of longitudinal ridges in long runout landslides has been proposed to require ice, as this low friction material would allow the spreading of the deposit, causing the development of longitudinal ridges by tensile deformation of the slide. However, ice-free laboratory experiments on rapid granular flows have demonstrated that longitudinal ridges can form as a consequence of helicoidal cells that generate from a mechanical instability, which onset requires a rough surface and a velocity threshold to be surpassed. Moreover, such experiments have showed that the wavelength of the longitudinal ridges is always 2 to 3 times the thickness of the flow.</p><p>We here present the results from three case studies: the 63-km-long Coprates Labe landslide in Valles Marineris on Mars; the 4-km-long El Magnifico landslide in Chile, Earth; and the 50-km-long Tsiolkovskiy crater landslide, at the far side of the Moon. We found that the wavelength of the longitudinal ridges is consistently 2 to 3 times the thickness of the landslide deposit, in agreement with experimental work on rapid granular flows. The recurrence of such scaling relationship suggests a scale- and environment-independent mechanism. We discuss the applicability of high-speed granular flow convection-style mechanisms to long runout landslides and speculate on the existence of an alternative vibration-assisted mechanism.</p>

scholarly journals Longitudinal ridges imparted by high-speed granular flow mechanisms in martian landslides

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Giulia Magnarini ◽  
Thomas M. Mitchell ◽  
Peter M. Grindrod ◽  
Liran Goren ◽  
Harrison H. Schmitt
Keyword(s):  
Granular Flow ◽  
High Speed ◽  
Transverse Velocity ◽  
Basal Layer ◽  
Mechanical Instability ◽  
Long Runout ◽  
Basal Ice ◽  
Scaling Relationship ◽  
Flow Mechanisms ◽  
Flow Experiments

Abstract The presence of longitudinal ridges documented in long runout landslides across our solar system is commonly associated with the existence of a basal layer of ice. However, their development, the link between their occurrence and the emplacement mechanisms of long runout landslides, and the necessity of a basal ice layer remain poorly understood. Here, we analyse the morphometry of longitudinal ridges of a martian landslide and show that the wavelength of the ridges is 2–3 times the average thickness of the landslide deposit, a unique scaling relationship previously reported in ice-free rapid granular flow experiments. We recognize en-echelon features that we interpret as kinematic indicators, congruent with experimentally-measured transverse velocity gradient. We suggest that longitudinal ridges should not be considered as unequivocal evidence for presence of ice, rather as inevitable features of rapid granular sliding material, that originate from a mechanical instability once a kinematic threshold is surpassed.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

Laboratory Simulation of Lunar Luminescence

1962 ◽  
Vol 14 ◽  
pp. 441-444 ◽  
Author(s):  
J. E. Geake ◽  
H. Lipson ◽  
M. D. Lumb
Keyword(s):  
Science And Technology ◽  
Laboratory Simulation ◽  
The Moon ◽  
Physics Department ◽  
Luminescent Spectrum

Work has recently begun in the Physics Department of the Manchester College of Science and Technology on an attempt to simulate lunar luminescence in the laboratory. This programme is running parallel with that of our colleagues in the Manchester University Astronomy Department, who are making observations of the luminescent spectrum of the Moon itself. Our instruments are as yet only partly completed, but we will describe briefly what they are to consist of, in the hope that we may benefit from the comments of others in the same field, and arrange to co-ordinate our work with theirs.

Formation of Lunar Craters and Bright Rays as a Result of Meteorite Impacts

1962 ◽  
Vol 14 ◽  
pp. 415-418
Author(s):  
K. P. Stanyukovich ◽  
V. A. Bronshten
Keyword(s):  
Explosive Charge ◽  
The Moon ◽  
Meteorite Impacts ◽  
The Earth ◽  
Lunar Craters ◽  
The Impact

The phenomena accompanying the impact of large meteorites on the surface of the Moon or of the Earth can be examined on the basis of the theory of explosive phenomena if we assume that, instead of an exploding meteorite moving inside the rock, we have an explosive charge (equivalent in energy), situated at a certain distance under the surface.

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

A Photographic Map of the Moon

1962 ◽  
Vol 14 ◽  
pp. 113-115
Author(s):  
D. W. G. Arthur ◽  
E. A. Whitaker
Keyword(s):  
Lunar Surface ◽  
The Moon ◽  
Map Projection

The cartography of the lunar surface can be split into two operations which can be carried on quite independently. The first, which is also the most laborious, is the interpretation of the lunar photographs into the symbolism of the map, with the addition of fine details from telescopic sketches. An example of this kind of work is contained in Johann Krieger'sMond Atlaswhich consists of photographic enlargements in which Krieger has sharpened up the detail to accord with his telescopic impressions. Krieger did not go on either to convert the photographic picture into the line symbolism of a map, or to place this picture on any definite map projection.

Probable Structure and Nature of the Formations on the Reverse Side of the Moon According to Photometric Measurements of Lunar Photographs

1962 ◽  
Vol 14 ◽  
pp. 39-44
Author(s):  
A. V. Markov
Keyword(s):  
The Moon ◽  
Probable Structure ◽  
The Earth ◽  
Interplanetary Station ◽  
Photometric Measurements ◽  
Automatic Interplanetary Station

Notwithstanding the fact that a number of defects and distortions, introduced in transmission of the images of the latter to the Earth, mar the negatives of the reverse side of the Moon, indirectly obtained on 7 October 1959 by the automatic interplanetary station (AIS), it was possible to use the photometric measurements of the secondary (terrestrial) positives of the reverse side of the Moon in the experiment of the first comparison of the characteristics of the surfaces of the visible and invisible hemispheres of the Moon.

Discovery and Measurement of Double Stars by Lunar Occultations

1965 ◽  
Vol 5 ◽  
pp. 28-37
Author(s):  
R. Edward Nather ◽  
David S. Evans
Keyword(s):  
The Moon ◽  
Double Stars ◽  
Stellar Diameters ◽  
Diffraction Effects

When a star is occulted by the dark limb of the Moon its apparent intensity drops to zero very quickly. MacMahon (1909) proposed that the time of disappearance would measure the diameter of the star, but Eddington (1909) demonstrated that diffraction effects at the lunar limb would lengthen the apparent time of disappearance to about 20 msec, and suggested that these effects would greatly limit the usefulness of the technique. MacMahon’s paper indicates that he was aware that stellar duplicity could be detected from occultation observations, but he did not amplify the point and Eddington did not comment on it. While it has been demonstrated theoretically by Williams (1939) and experimentally by Whitford (1939) and others that stellar diameters of a few arcmsec can be measured by this technique, its use for the discovery and measurement of double stars has been only incidental to other programs (O’Keefe and Anderson, 1952; Evanset al., 1954). Properly exploited, the method can contribute materially to the study of double stars.

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