Chandrayaan-1 observation of distant secondary craters of Copernicus exhibiting central mound morphology: Evidence for low velocity clustered impacts on the Moon

2011 ◽  
Vol 59 (9) ◽  
pp. 870-879 ◽  
Author(s):  
P. Senthil Kumar ◽  
A. Senthil Kumar ◽  
V. Keerthi ◽  
J.N. Goswami ◽  
B. Gopala Krishna ◽  
...  
Keyword(s):  
The Moon ◽  
Low Velocity ◽  
Mound Morphology

Travel times of body waves in the moon

1970 ◽  
Vol 60 (1) ◽  
pp. 63-78 ◽  
Author(s):  
Yosio Nakamura ◽  
Gary V. Latham
Keyword(s):  
Large Amplitude ◽  
Body Waves ◽  
Central Core ◽  
Travel Times ◽  
The Moon ◽  
Shadow Zone ◽  
Low Velocity ◽  
Low Velocity Zone ◽  
Velocity Zone

abstract Travel times and amplitudes of body waves in lunar models have been computed. The effect of a low-velocity zone upon the travel times and amplitudes of body waves is likely to be small unless the condition for the existence of a shadow zone at short to moderate epicentral distances is nearly satisfied. The PKP phase from a possible central core of the moon is likely to have a large amplitude in the area opposite to the epicenter.

MiniPINS - Miniature Planetary In-situ Sensors

2020 ◽  
Author(s):  
Maria Genzer ◽  
Maria Hieta ◽  
Antti Kestilä ◽  
Harri Haukka ◽  
Ignacio Arruego ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Technology Development ◽  
Martian Atmosphere ◽  
Target Velocity ◽  
The Moon ◽  
Martian Surface ◽  
Low Velocity ◽  
Science Data ◽  
Finnish Meteorological Institute ◽  
Thermal Environments

<p>MiniPINS is an ESA study led by the Finnish Meteorological Institute to develop and prototype miniaturised surface sensor packages (SSPs) for Mars and the Moon. The study aims at miniaturising the scientific sensors and subsystems, as well as identifying and utilizing commonalities of the packages, allowing to optimise the design, cut costs and reduce the development tim<span>e. We present the Preliminary Mission Plan and possible concepts for the landers for this mission. </span></p><p>The Mars SSP will be a small 25 kg penetrator deployed from Mars orbit. Maximally four (4) penetrators will be carried to the Martian orbit by an Orbiter and the Orbiter will be oriented for deployment of each penetrator. In the Martian atmosphere the penetrators undergo aerodynamic braking until they reach the target velocity for entering the Martian surface. </p><p>The SSPs will start their scientific observations after landing and stay stationary throughout their mission (2 years). The SSPs have an ambitious science program to study for example the Martian atmosphere, seismology, magnetic field and chemistry. Theri payloads consist of a camera, a visual spectrometer, a meteorological package, an accelerometer, thermoprobes, a magnetometer, a chemistry package and a radiation monitor. The SSP will also provide positioning signal and communications link to the Orbiter.<span> </span></p><p>The Moon SSP will be a miniature 5 kg station deployed on the Moon surface by a rover. Maximum four (4) SSPs are deployed with low velocity and small impact depth (max. 0.05 m). All SSPs can be deployed from a single rover on the same sortie. The SSPs will start their scientific observations after landing and study for example radiation, seismology, magnetic field and chemistry. SSP will also provide communications link either to the rover or to a relay orbiter.<span> </span></p><p>Both Mars and Moon SSPs will be miniaturised, light and robust, and still capable of surviving high G loads and extreme thermal environments. SSPs are capable of working on the surface of Mars or Moon and to produce high quality science data with state of art instrumentation. The output of this work will enable ESA to prepare and plan for technology development programs required to implement such ambitious planetary missions.<span> </span></p>

Lunar secondary craters: Results for secondary sizes across the Moon, and size-velocity distributions of ejected blocks

2020 ◽  
Author(s):  
Kelsi Singer ◽  
William McKinnon ◽  
Bradley Jolliff
Keyword(s):  
Fragment Size ◽  
Ejection Velocity ◽  
Escape Velocity ◽  
The Moon ◽  
Secondary Field ◽  
Low Velocity ◽  
Lunar Reconnaissance Orbiter ◽  
Secondary Crater ◽  
Wide Angle Camera ◽  
The Impact

<p>Planetary impact events eject large volumes of surface material.  Crater excavation processes are difficult to study, and in particular the details of individual ejecta fragments are not well understood.  A related, enduring issue in planetary mapping is whether a given crater resulted from a primary impact (asteroid or comet) or instead is a secondary crater created by an ejecta fragment.  With mapping and statistical analyses of six lunar secondary crater fields we provide three new constraints on these issues: 1) definition of the maximum secondary crater size as a function of distance from a primary crater on the Moon, 2) estimation of the size and velocity of ejecta fragments that formed these secondaries, and 3) estimation of the fragment size ejected at escape velocity. </p><p>We mapped secondary craters around primary craters ranging in size from ~0.83–660 km in diameter using Lunar Reconnaissance Orbiter Camera (LROC) Narrow and Wide Angle Camera images.  Identification of secondary craters was based on expected secondary crater morphologies (e.g., v-shaped ejecta, clusters or chains, and elongation in the direction radial to the primary, similarity in degradation state across the secondary field) and secondaries were assigned a confidence level (as to whether they were likely a secondary crater) based on the number of expected morphologies they displayed.  Only the most confident features were utilized in this work, as there is no way to capture all secondary craters within a given lunar secondary field.  Scaling from secondary crater sizes to ejecta fragment sizes was carried out using the Housen-Holsapple-Schmidt formulations.                                                                                                                          </p><p>The largest secondaries and those made by the highest velocity fragments (up to ~1.4 km/s) were mapped around the Orientale basin.  The estimated size of fragments that could reach the lunar Hill-sphere escape velocity of 2.34 km/s varies by the size of the impact event, but could be as large as ~850 m for Orientale.  Note that these are not necessarily expected to be coherent fragments, they could also be loosely bound collections of smaller fragments.  However, the fragments/clumps mapped here remained in a form that resembles a single fragment in order to form the distinct secondary craters observed.  For low velocity secondaries, surprisingly, we found features that appear to be secondary craters formed from fragments with velocities as small as 50 m/s around the smallest primary.  </p><p>Through this analysis, we confirmed and extended a suspected scale-dependent trend in ejecta size-velocity distributions.  Maximum ejecta fragment sizes fall off much more steeply with increasing ejection velocity for larger primary impacts (compared to smaller primary impacts).  Specifically, we characterize the maximum ejecta sizes for a given ejection velocity with a power law, and find the velocity exponent varies between approximately -0.3 and -3 for the range of primary craters investigated here.  Data for the jovian moons Europa and Ganymede confirm similar trends for icy surfaces.  This result is not predicted by analytical theories of formation of Grady-Kipp fragments or spalls during impacts, and suggests that further modeling investigations are warranted to explain this scale-dependent effect.</p>

scholarly journals Creep in the Earth and Planets (Invited Lecture)

1972 ◽  
Vol 48 ◽  
pp. 1-9 ◽  
Author(s):  
Harold Jeffreys
Keyword(s):  
Thermal Instability ◽  
Continental Drift ◽  
Free Vibrations ◽  
The Moon ◽  
Low Velocity ◽  
Outstanding Problem ◽  
The Earth ◽  
Linear Rule ◽  
Constant Shear Stress ◽  
Logarithmic Rule

An outstanding problem is to reconcile the Moon's rotation with the persistence of its non-hydrostatic dynamical ellipticities. The first requires imperfection of elasticity under strains of order 10−7; the second apparently little under larger ones.Lomnitz gave experimental evidence that creep is linear at elastic shears from 10−5 to 10−4, indicating that a linear rule could be right at still smaller values. Positive evidence for the Earth comes from the damping of the 14-monthly nutation, which has a relaxation time of the order of 30 yr. Most work on imperfect elasticity has assumed that under constant shear stress the strain increases with time either like t (elasticoviscosity) or like logt. If the result from the 14-monthly nutation, with elasticoviscosity, is applied to the Moon, the dynamical ellipticities would have subsided considerably in the last 200 yr. With the logarithmic rule an S pulse at 80° would have its beginning spread out over about 70 s and be unreadable. These contradictions are avoided if the increase under constant stress is about like t0.2. The resulting law involves two constants. Without change of these, applications are made to other phenomena. The rotations of the Moon and of other satellites whose rotations are known are explained; so is the persistence of the Moon's dynamical ellipticities; also the failure to detect three free oscillations that might theoretically exist. Elasticoviscosity would imply rapid disappearance of the non-hydrostatic second and third harmonics in the Earth's gravitational field; this is avoided with the new law. Study of damping of free vibrations of the Earth (including surface waves) has usually assumed the logarithmic law, but it appears that the new law fits the data at least as well, and that it may also explain those that have been interpreted in favour of layers of low velocity. It appears that the damping at depths up to 400 km or so is much more severe than the average for the Earth's shell, and more evidence for shorter periods is much needed.Any law with an index less than 1 would forbid thermal instability (convection) and continental drift.

Motions of neutral hydrogen at high latitudes

1967 ◽  
Vol 31 ◽  
pp. 265-278 ◽  
Author(s):  
A. Blaauw ◽  
I. Fejes ◽  
C. R. Tolbert ◽  
A. N. M. Hulsbosch ◽  
E. Raimond
Keyword(s):  
Surface Density ◽  
Velocity Dispersion ◽  
Neutral Hydrogen ◽  
Hydrogen Gas ◽  
High Latitudes ◽  
Low Velocity

Earlier investigations have shown that there is a preponderance of negative velocities in the hydrogen gas at high latitudes, and that in certain areas very little low-velocity gas occurs. In the region 100° <l< 250°, + 40° <b< + 85°, there appears to be a disturbance, with velocities between - 30 and - 80 km/sec. This ‘streaming’ involves about 3000 (r/100)2solar masses (rin pc). In the same region there is a low surface density at low velocities (|V| < 30 km/sec). About 40% of the gas in the disturbance is in the form of separate concentrations superimposed on a relatively smooth background. The number of these concentrations as a function of velocity remains constant from - 30 to - 60 km/sec but drops rapidly at higher negative velocities. The velocity dispersion in the concentrations varies little about 6·2 km/sec. Concentrations at positive velocities are much less abundant.

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.

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