scholarly journals Survival of fossils under extreme shocks induced by hypervelocity impacts

2014 ◽  
Vol 372 (2023) ◽  
pp. 20130190 ◽  
Author(s):  
M. J. Burchell ◽  
K. H. McDermott ◽  
M. C. Price ◽  
L. J. Yolland
Keyword(s):  
Peak Pressure ◽  
Fragment Size ◽  
Hypervelocity Impact ◽  
The Moon ◽  
Hypervelocity Impacts ◽  
The Earth ◽  
Giant Impacts ◽  
The Mean ◽  
Peak Pressures ◽  
Impact Experiments

Experimental data are shown for survival of fossilized diatoms undergoing shocks in the GPa range. The results were obtained from hypervelocity impact experiments which fired fossilized diatoms frozen in ice into water targets. After the shots, the material recovered from the target water was inspected for diatom fossils. Nine shots were carried out, at speeds from 0.388 to 5.34 km s −1 , corresponding to mean peak pressures of 0.2–19 GPa. In all cases, fragmented fossilized diatoms were recovered, but both the mean and the maximum fragment size decreased with increasing impact speed and hence peak pressure. Examples of intact diatoms were found after the impacts, even in some of the higher speed shots, but their frequency and size decreased significantly at the higher speeds. This is the first demonstration that fossils can survive and be transferred from projectile to target in hypervelocity impacts, implying that it is possible that, as suggested by other authors, terrestrial rocks ejected from the Earth by giant impacts from space, and which then strike the Moon, may successfully transfer terrestrial fossils to the Moon.

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.

scholarly journals The mean distance to the Moon as determined by radar

1965 ◽  
Vol 21 ◽  
pp. 81-93 ◽  
Author(s):  
B. S. Yaplee ◽  
S. H. Knowles ◽  
A. Shapiro ◽  
K. J. Craig ◽  
D. Brouwer
Keyword(s):  
The Moon ◽  
The Earth ◽  
Lunar Topography ◽  
Radar Measurements ◽  
The Mean

The results of 1959-1960 radar measurements of the distance of the Moon are given. The method of reduction of the data is described The possible effects of lunar topography and errors of other origins are discussed, as well as the effects of different constants such as the radii of the Earth and of the Moon.

I. Dynamical considerations - Dynamics of the Moon

1967 ◽  
Vol 296 (1446) ◽  
pp. 245-247 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Uniform Density ◽  
The Moon ◽  
Homogeneous Body ◽  
Cubic Form ◽  
The Earth ◽  
Change Of State ◽  
Rate Of Increase ◽  
The Mean ◽  
Single Material

We know the mass of the Moon very well from the amount it pulls the Earth about in the course of a month; this is measured by the resulting apparent displacements of an asteroid when it is near us. Combining this with the radius shows that the mean density is close to 3.33 g/cm 3 . The velocities of earthquake waves at depths of 30 km or so are too high for common surface rocks but agree with dunite, a rock composed mainly of olivine (Mg, Fe II ) 2 SiO 4 . This has a density of about 3.27 at ordinary pressures. The veloci­ties increase with depth, the rate of increase being apparently a maximum at depth about 0.055 R in Europe and 0.075 R in Japan. It appeared at one time that there was a discontinuity in the velocities at that depth, corresponding to a transition of olivine from a rhombic to a cubic form under pressure. It now seems that the transition, though rapid, is continuous, presumably owing to impurities, but the main point is that the facts are explained by a change of state, and that the pressure at the relevant depth is reached nowhere in the Moon, on account of its smaller size. There will, however, be some compression, and we can work out how much it would be if the Moon is made of a single material. It turns out that the actual mean density of the Moon would be matched if the density at atmospheric pressure is 3.27—just agreeing with the specimen of dunite originally used for comparison. The density at the centre would be 3.41. Thus for most purposes the Moon can be treated as of uniform density. With a few small corrections the ratio 3 C /2 Ma 2 would be 0.5956 ± 0.0010, as against 0.6 for a homogeneous body. To make it appreciably less would require a much greater thickness of lighter surface rocks than in the Earth.

Four-View Split-Image Fragment Tracking in Hypervelocity Impact Experiments

2019 ◽  
Author(s):  
Erkai Watson ◽  
Nico Kunert ◽  
Robin Putzar ◽  
Hans-Gerd Maas ◽  
Stefan Hiermaier
Keyword(s):  
High Speed ◽  
Particle Tracking Velocimetry ◽  
Space Debris ◽  
Particle Image ◽  
Hypervelocity Impact ◽  
Hypervelocity Impacts ◽  
Image Fragment ◽  
Image Velocimetry ◽  
The Individual ◽  
Impact Experiments

Abstract Hypervelocity impacts (HVI) often cause significant fragmentation to occur in both target and projectile materials, and is often encountered in space debris and planetary impact applications [1]–[5]. In this paper, we focus on determining the individual velocities and sizes of fragments tracked in high-speed images. Inspired by velocimetry methods such as Particle Image Velocimetry (PIV) [6] and Particle Tracking Velocimetry (PTV) [7] and building on past work [8], we describe the setup and algorithm used for measuring fragmentation data.

scholarly journals On The lunar Secular Acceleration: A Possible Approach

1990 ◽  
Vol 141 ◽  
pp. 201-202
Author(s):  
V. Protitch-Benishek
Keyword(s):  
Celestial Mechanics ◽  
Numerical Evaluation ◽  
Quadratic Term ◽  
The Moon ◽  
Moon System ◽  
Secular Acceleration ◽  
Mean Motion ◽  
The Earth ◽  
Exact Agreement ◽  
The Mean

The secular quadratic term in the expression of the Moon's longitude has been introduced empirically after the conclusion that its mean motion is not constant (Halley, 1695).But, the explanation of this term and also of its numerical evaluation presented and still presents in our time great difficulties. All efforts, namely, to obtain an exact agreement between observed and theoretical value of Moon's secular acceleration were unsuccessful: the first of these two values exceeds always the second one by a very large amount. This discordance and unexplained residuals (O – C) in the mean longitude of the Moon gave rise finally to the statement that these are due to a retardation and irregularity in the Earth's rotation. But, after hardly a fifty years, this hypothesis revealed even more new difficulties and questions concerning also the problem of stability of the Earth-Moon system. It seems that there is a true reason for which this problem occurs as one of the unsolved problems of Celestial Mechanics (Brumberg and Kovalevsky, 1986; Seidelmann, 1986).

scholarly journals A first analysis of the mean motion of CHAMP

2003 ◽  
Vol 1 ◽  
pp. 95-101
Author(s):  
F. Deleflie ◽  
P. Exertier ◽  
P. Berio ◽  
G. Metris ◽  
O. Laurain ◽  
...  
Keyword(s):  
Orbital Motion ◽  
Surface Forces ◽  
The Moon ◽  
Orbital Elements ◽  
Champ Satellite ◽  
Mean Motion ◽  
The Earth ◽  
The Mean ◽  
Low Altitude

Abstract. The present study consists in studying the mean orbital motion of the CHAMP satellite, through a single long arc on a period of time of 200 days in 2001. We actually investigate the sensibility of its mean motion to its accelerometric data, as measures of the surface forces, over that period. In order to accurately determine the mean motion of CHAMP, we use “observed" mean orbital elements computed, by filtering, from 1-day GPS orbits. On the other hand, we use a semi-analytical model to compute the arc. It consists in numerically integrating the effects of the mean potentials (due to the Earth and the Moon and Sun), and the effects of mean surfaces forces acting on the satellite. These later are, in case of CHAMP, provided by an averaging of the Gauss system of equations. Results of the fit of the long arc give a relative sensibility of about 10-3, although our gravitational mean model is not well suited to describe very low altitude orbits. This technique, which is purely dynamical, enables us to control the decreasing of the trajectory altitude, as a possibility to validate accelerometric data on a long term basis.Key words. Mean orbital motion, accelerometric data

scholarly journals Mesoscale modeling and debris generation in hypervelocity impacts

2019 ◽  
Author(s):  
Stephanie N. Q. Bouchey ◽  
Jeromy T. Hollenshead
Keyword(s):  
Experimental Data ◽  
Fragment Size ◽  
Infinite Plate ◽  
Hypervelocity Impact ◽  
Mesoscale Modeling ◽  
Strain Rates ◽  
Hypervelocity Impacts ◽  
Modeling Approach ◽  
Grain Properties ◽  
Material Temperature

Abstract Material fragmentation after a hypervelocity impact is of interest to predictive electro-optical and infrared (EO/IR) modeling. Successful comparisons with data require that submicron fragments are generated in such impacts; however, experimental data has so far been unable to produce fragments of this scale [e.g., 1-3]. This effort investigated the generation of predicted debris from hypervelocity impact of a sphere on a flat, semi-infinite plate. It is hypothesized that explicit modeling of grains, especially in the presence of void and varying grain properties, may lead to differences in predicted strain rates (locally higher) associated with the grain boundaries. Such an effect may lead to smaller predicted fragments sizes than when using the traditional bulk modeling approach and may provide improved understanding of fragmentation modeling in hypervelocity impacts. Comparisons of predicted strain rates at failure (a proxy for fragment size) and material temperature were made between simulations run using a bulk modeling approach and a mesoscale grain modeling approach.

scholarly journals TRAJECTORY BASED 3D FRAGMENT TRACKING IN HYPERVELOCITY IMPACT EXPERIMENTS

2018 ◽  
Vol XLII-2 ◽  
pp. 1175-1181 ◽  
Author(s):  
E. Watson ◽  
H.-G. Maas ◽  
F. Schäfer ◽  
S. Hiermaier
Keyword(s):  
Measurement Technique ◽  
Experimental Measurement ◽  
High Speed ◽  
Space Debris ◽  
Hypervelocity Impact ◽  
Experimental Setup ◽  
Velocity Data ◽  
Hypervelocity Impacts ◽  
Impact Experiment ◽  
Impact Experiments

Collisions between space debris and satellites in Earth’s orbits are not only catastrophic to the satellite, but also create thousands of new fragments, exacerbating the space debris problem. One challenge in understanding the space debris environment is the lack of data on fragmentation and breakup caused by hypervelocity impacts. In this paper, we present an experimental measurement technique capable of recording 3D position and velocity data of fragments produced by hypervelocity impact experiments in the lab. The experimental setup uses stereo high-speed cameras to record debris fragments generated by a hypervelocity impact. Fragments are identified and tracked by searching along trajectory lines and outliers are filtered in 4D space (3D + time) with RANSAC. The method is demonstrated on a hypervelocity impact experiment at 3.2 km/s and fragment velocities and positions are measured. The results demonstrate that the method is very robust in its ability to identify and track fragments from the low resolution and noisy images typical of high-speed recording.

scholarly journals On the Growth of the Earth-Moon System

1974 ◽  
Vol 3 ◽  
pp. 469-473
Author(s):  
F. L. Whipple
Keyword(s):  
Solar Nebula ◽  
Low Density ◽  
Differentiation Process ◽  
The Moon ◽  
Moon System ◽  
Hypervelocity Impacts ◽  
The Earth ◽  
Refractory Minerals ◽  
Gravitational Capture ◽  
Two Bodies

This paper elaborates the postulate that the Earth and Moon became a binary system during their accretional development and that the Moon’s growth was essentially completed before the assumed solar nebula dissipated. The solar nebula was still hot enough at the formation of the two bodies that both consisted largely of the refractory and relatively low-density minerals now characteristic of the Moon. During the subsequent condensation, agglomeration and accretion of siderophile and more volatile higher density minerals, the Earth grew very much faster than the Moon because of (a) its much greater gravitational capture area coupled with retention by a sizeable atmosphere and (t>) the Moon’s velocity, with respect to the solar nebula, which produced a wind that aerodynamically blew away volatiles and smaller debris resulting from hypervelocity impacts of larger planetesimals. This ‘impact differentiation’ process favored the retention of the refractory minerals on the Moon (Figure 1). The Moon’s surprisingly high moment of inertia follows naturally from the basic postulate.

scholarly journals On the Absolute Orientation of the Selenodetic Reference Frame

1981 ◽  
Vol 63 ◽  
pp. 281-286
Author(s):  
V. S. Kislyuk
Keyword(s):  
Coordinate System ◽  
Center Of Mass ◽  
The Moon ◽  
Coordinate Systems ◽  
Inertial Coordinate System ◽  
Reference Coordinate System ◽  
The Earth ◽  
Principal Axes ◽  
The Mean ◽  
Selection Of

The selection of selenodetic reference coordinate system is an important problem in astronomy and selenodesy. For the purposes of reduction of observations, planning and executing space missions to the Moon, it is necessary, in any case, to know the orientation of the adopted selenodetic reference system in respect to the inertial coordinate system.Let us introduce the following coordinate systems: C(ξc, ηc, ζc), the Cassini system which is defined by the Cassini laws of the Moon rotation;D(ξd, ηd, ζd), the dynamical coordinate system, whose axes coincide with the principal axes of inertia of the Moon;Q(ξq, ηq, ζq), the quasi-dynamical coordinate system connected with the mean direction to the Earth, which is shifted by 254" West and 75" North from the longest axis of the dynamical system (Williams et al., 1973);S(ξs, ηs, ζs), the selenodetic coordinate system, which is practically realized by the positions of the points on the Moon surface given in Catalogues;I(X,Y,Z), the space-fixed (inertial) coordinate system. All the systems are selenocentric with the exception of S(ξs, ηs, ζs On the whole, the origin of this system does not coincide with the center of mass of the Moon.

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