The studies carried out on the Luna 16 regolith have confirmed the data that were already published internationally. By means of activation analysis under irradiation in the reactor, activation analysis with a 14 MeV U-generator, and mass spectroscopy on samples of 10 or 20 mg, six main and 63 trace elements were quantitatively determined and compared with known data

Bankwitz, E.

Bankwitz, P.

Schoen, J.

Stiller, H.

Vollstaedt, H.

Wagner, F. C.

Wasch, R.

English

NASA Technical Reports Server

Results of Special Mechanical Analyses of
Luna 16 Material1
H. Stiller, H. Vollstadt, R. Wasch, P. Bankwitz,
E. Bankwitz, and F. C. Wagner
Akademie der Wissenschaften der DDR,
Zentralinstitut fur Physik der Erde,
Potsdam, East Germany
J. Schon
Bergakademie Freiberg
Sektion Geowissenschaften
Freiberg (Sa), East Germany
For the analysis of lunar soil samples in
the GDR, under the direction of the GDR
Academy of Sciences, a special methodologi-
cal system for the examination of the rego-
lith has been developed by selected scientific
institutions of the Academy of Sciences and
some universities. This system consists of the
following complex branches:
1. Examination of fractured or split
structures for mineral grains or glass
grains
2. Consideration of the pressure-depen-
dence of the propagation velocity of
elastic waves in lunar rock samples
3. Investigation of the structural be-
havior of lunar minerals and glasses
under normal thermodynamic condi-
tions and at high pressures
4. Electron-optical study of the regolith
to clarify mineralogical and crystal-
lographic properties of selected mate-
rials
5. Studies into the mineralogy and crys-
tallography of the rock-forming min-
erals and the petrochemistry of the
lunar soil samples
6. Determination of main and trace ele-
ments by means of a methodology
oriented to very small samples (plus
1
 Central Earth Physics Institute report No. 409.
determination of isotopes, isotopic
abundances, and isotopic ratios)
7. Gamma-ray spectroscopic analyses of
the radioactivity of the Luna 16
regolith
This methodological system forms the
basis of a general scheme consisting mainly
of comparative studies of lunar and ter-
restrial rocks: lunar materials and corre-
sponding analogous terrestrial materials are
analyzed in the same way and with the same
objective, and the results obtained are
brought into the discussion and interpreta-
tion of geophysical, physical, chemical, and
mineralogical problems of the Earth and the
Moon.
For comparative studies of the physico-
mechanical behavior of lunar and terrestrial
rocks, it is essential that the chemical and
mineralogical parameters be known. The
studies carried out on the Luna 16 regolith
to find these have confirmed the data that
were already published internationally. For
example, by means of activation analysis un-
der irradiation in the reactor, activation
analysis with a 14 MeV U-generator, and
mass spectroscopy on samples of 10 or 20
mg, six main and 63 trace elements were
quantitatively determined and compared with
known data (ref. 1).
697
https://ntrs.nasa.gov/search.jsp?R=19780005026 2020-03-22T06:49:03+00:00Z
698 COSMOCHEMISTRY OF THE MOON AND PLANETS
Mineralogical and crystallographic studies
confirmed that in addition to glass of the
most varied composition, mainly olivine,
pyroxene, and plagioclase occur (ref. 2). The
results of the chemical and mineralogical-
crystallographic studies show that the prop-
erties and behavior of lithogenetic minerals
found on the Moon basically correspond to
those of analogous minerals on the Earth
(refs. 3 and 4). Nevertheless, the thermo-
dynamic conditions peculiar to the Moon, i.e.,
absence of free water, vacuum, and mechani-
cal stress through meteorite impacts, etc.,
ought to have an effect on the rocks forming
the upper strata of the Moon. The mechanical-
elastic behavior in particular can be affected
by these parameters. The extent to which
this applies to minerals and glasses can be
shown in part by the following studies
(ref. 5).
Analysis of Fracture and Cleavage
Surfaces of Lunar Mineral
and Glass Fragments
The mineral and glass fragments used for
these studies are between 0.02 and 0.2 mm in
diameter and correspond, "terrestrially"
speaking, to the fine sand fraction. The ex-
amination of structures for fracture surfaces
is justified in that they are a documentation
of (1) the course of events in processes of
rupture; (2) surface formations differing in
age; and (3) the nature of rupture processes
(especially their speed) from which, to a
certain extent, further information can be
obtained as to the causes of rupture.
These experiments are therefore very suit-
able for the examination of fracture concepts
developed on terrestrial material—and in
this case on rocks as well—which we have
been studying for a long time. Particular
features of the fracture surfaces (in rock
ruptures the so-called joint structures) give
an indication as to the nature of the process
of rupture: surface steps radiate from the
starting point of the crack, their divergence
indicating the direction of propagation.
These surface steps can also turn into inde-
pendent secondary fracture surfaces. They
are evidence of the propagation of a fracture
at different levels.
A conclusion can also be drawn as to the
fracture propagation velocity. It is known
from fracture physics that the propagation of
a fracture usually occurs rapidly (slow fa-
tigue fractures are clearly distinguishable).
It can also be deduced from the physical na-
ture of the rupture process that certain sur-
face structures, as well as a rupture process
itself, are genetically related to the propaga-
tion, refraction, etc., of elastic waves, and
that the fracture propagation velocity, being
about half the transverse wave velocity, is
relatively high. Interruptions in fissuration
are marked in particular by initial fields
lying in series.
Following is an example to explain the
method of work and the object of the investi-
gation. Figure 1 shows a regolith grain (a),
Figure 1.—Analysis of fracture of a regollth-grain.
MECHANICAL ANALYSES OF LUNA 16 MATERIAL 699
with two detailed sketches (b + c). Owing
to the coarse internal structure, the individ-
ual surfaces are unevenly formed, while (b)
shows the interrelationship of the ages of the
fracture surfaces, (c) shows the centers of
cracking and the directions of cracking of
the surface portions.
(1) T! and I2 are initial points that have
occurred simultaneously because
their structures of rupture interlock
at their line of intersection.
(2) Since C and D on surface B form
steep steps, it can be assumed that B
is older than C and D. The struc-
tures of E develop from D, i.e., E
developed after D.
(3) From two secondary initial points, I2,
the process of fracture propagation
from D to E can be seen (in b). A is
a mineralized rupture. One suspects
that A and B belong to older surface
systems while C, D, and E represent
a younger system. Figures 2 and 3
show further examples of fracture
surface analysis.
Unlike geologically comparable material,
the regolith from Luna 16 is very finely di-
vided. On the surface of the Earth, this oc-
curs only in areas of mylonite. In addition,
despite the fineness, the regularity of the
larger particles is remarkable. This indicates
fracture-producing impacts at fairly large
distances. Finally, such a fine disintegration
is bound to absorb considerably all continu-
ous elastic waves. The materials under re-
view can reliably be said to have low wave
velocities. From the first results obtained up
to now the following can be stated: the frac-
ture structures formed on the Moon corre-
spond in all respects to those that have
developed on the Earth. The rupture pro-
cesses must therefore also be the same. It can
be assumed that the formation of fractures
in crystals, glasses, breccias, etc., took place
in a vacuum and in the absence of free water.
Both factors clearly have no decisive pri-
mary importance for the rupture process it-
self.
Fracture surface structures are a result
Figure 2.—Example 2 of fracture surface analysis.
0,25 mm
Figure 3.—Example 3 of fracture surface analysis.
700 COSMOCHEMISTRY OF THE MOON AND PLANETS
of the dissipation of energy in the form of
waves. The formation of every microcrack
and of every fissure represents a tremor of
the very smallest magnitude. In the Luna 16
regolith, the final forms that predominate
suggest a highly intense or explosive rupture.
It still remains to be investigated to what
extent changes in the internal structure of a
material are manifested in different changes
in the form of the fracture structures typical
for the particular case; to what extent one
can infer internal structural features—for
rocks as well—from small differences in the
formation of the fracture structure; and how
these structural features affect the rupture
process of individual rock constituents.
Examination of the Pressure-
Dependence of the
Propagation Velocity of
Elastic Waves in Lunar
and Terrestrial Rocks
The behavior of the propagation velocity of
elastic waves particularly longitudinal waves
in this case under increasing pressure found
through examination of dense Moon rock
samples can be compared with that found
for terrestrial rocks. Such comparison shows
that (1) lunar rock samples demonstrate a
far greater pressure-dependence than ter-
restrial rock samples of comparable density
and chemistry and (2) at low pressures in
particular, the velocities of the lunar samples
are far below those of the comparable terres-
trial samples. Possible causes of the pressure-
dependence are changes in the elastic prop-
erties of the minerals themselves and changes
in pore or fissure volume.
Even with the high density of the material
of p = 3.1 g/cm3, neither of these causes can
explain the considerable changes in velocity
with increasing pressure. It is more likely
that the reason for this dependence is to be
found in the occurrence of "imperfectly elas-
tic bonds between the rock constituents."
These defects, e.g., in grain or mineral con-
tacts, are not necessarily tied to a "fissure
volume" worth mentioning. The theoretical
treatment of this problem leads to the fol-
lowing considerations.
A quantity K, can be taken as a coefficient
of measure for the cracks in the rocks de-
scribed. K0 characterizes the imperfect bond
between the rock constituents caused by
cracks. K0 can be expressed by analytical
formula corresponding to Stiller et al. (ref.
7). Taking into account this K0 parameter, a
velocity-pressure relation of the following
can be obtained :
VP = VF(1 -K0e-*<T*
where VP = velocity of longitudinal waves of
the sample under pressure
Vr = velocity of the flawless compact
substance
K0 = initial value of quantity K, i.e.,
K at a pressure of a — 0 kg/cm2
A = coefficient for the deformability
of the sample
Figure 4 shows the dependence
on a double logarithmic scale. The double
logarithmic representation makes it possible
to use the curves as "master curves" for the
interpretation of experimental results. The
measured values are drawn on paper of the
same scale as that of the master curve ; this
is then placed over the master curve, and an
attempt is made, by moving the paper and
keeping the axes parallel, to bring the mea-
sured values into coincidence with the master
curve.
Figure 4.—Function VP/Vr = (1 - K&-*')"' in dou-
ble logarithmic scale.
MECHANICAL ANALYSES OF LUNA 16 MATERIAL 701
A)
B)
t = wtocif/ of ample under pressure loading lol
if = velocity of the unfiultf compact ample
K0 = initial tilae of K it tf=0 kp/cm2
4 = coefficient including the deformitnlitf of simple
10° 102
Figure 5.—Experimental results of terrestrial and
lunar rocks, evaluated from the relation under A:
curve 1 dunite (terrestrial)^ 2.31 gem'1; 2 chloritic
schists (terrestrial) = 2.84 gem''; 3 gneiss (ter-
restrial) — 2.72 gem'1; 4. basalt (lunar) = S.S2
gem-'.
U 7
I 6jx
5
4
-cHI-
103 W4
Figure 6. — Experimental results of lunar rocks:
curve 1 basalt = 3.32 gem'*; curve 2 basalt — S.18
gem'3; curve 3 basalt = 2.88 . . . 3.38 gem'1; curve
4 breccia = 2.35 gem''
Figure 5 shows this velocity relation (A)
and the results of such an interpretation, ob-
tained from lunar and terrestrial samples
(B). In part (B), curves 1, 2, and 3 for ter-
restrial rocks show K0 values up to 0.6 (for a
gneiss with density p = 2.72 g/cnr3). The re-
sults for a lunar sample much denser in com-
parison (curve 4) show an even higher value
for K0 = 0.8, and therefore indicate extreme
internal crushing of the rock.
Apart from the curve parameter K0, the
comparison of the calculated and the mea-
sured value at a = 1 kg/cnr2 and the value
for VF marked by an arrow on the velocity
axis are also given. This value VF is the ordi-
nate value on the experimental curve, corre-
sponding to the ordinate value VP/VF = 1 on
the calculated curves. Of particular interest
here is the good agreement in the VF values
between the terrestrial dunite (curve 1) and
the lunar "basalt" (curve 4). This underlines
the fact that the differences in elastic be-
havior do not result primarily from the
mineralogical composition, but from the na-
ture and degree of the internal bonds. In
figure 6, the evaluations of experimental
results for lunar rocks are shown. They con-
firm the assumptions made so far. The
considerable internal disturbance in the
bonds between the constituents of the lunar
rocks will most probably have been mainly
caused by a heavy alternating thermal stress
and also a very heavy mechanical stress (me-
teorite impacts—shock waves). Berzov et al.
(ref. 6) brings these last influences together
under the heading "impact metamorphosis."
Conclusions
The following conclusions can be drawn from
the studies carried out so far:
1. The lithogenetic minerals on the sur-
face of the Moon correspond in most
respects to their terrestrial counter-
parts, as can be deduced from chemi-
cal, mineralogical, radiographic, and
electronoptical examinations.
2. The mechanical short-term behavior
also conforms to this trend.
3. From this it can be deduced that the
special thermodynamic conditions on
the Moon have no appreciable influ-
ence on the physico-mechanical be-
havior of lunar minerals, although
there are some significant differences
702 COSMOCHEMISTRY OF THE MOON AND PLANETS
in the distribution of elements.
4. This influence, however, makes itself
felt more in the behavior of the lunar
rocks, since in contrast to terrestrial
conditions lunar rock has been subject
to extreme dynamic influence. This is
manifest in, among other things, a con-
siderably greater pressure-dependence
—above all at low pressures—of the
velocity of longitudinal waves. The
causes for this can be found in the rela-
tively high degree of crushing in lunar
rocks caused by meteorite impacts and
other types of mechanical stress; this
was substantiated quantitatively.
5. This mechanical influence has meant
that the grain contacts and all other
possibilities of connection between
the rock constituents (minerals, glass)
have not attained the "perfection"
which predominates, for example, in
most terrestrial rocks.
6. The results have shown that the
physico-mechanical state of lunar rocks
can be expressed as a formula on the
basis of known dependences.
7. The velocity-pressure dependences of
lunar rocks, corrected with regard to
the crushing factor, behave quan-
titatively and qualitatively like the
corresponding terrestrial rocks. Conse-
quently, the velocity-depth dependences
in the Moon at sufficient depth must be
analogous to the corresponding depth
dependences in the Earth, as can also
be seen from the results of lunar seis-
mology (see ref. 8).
8. The analogies of physico-mechanical
behavior mentioned above make it pos-
sible to use adequate equations of state
for the Moon as well.
References
1. BRUNNER, G., Bestimmung Chemischer Elemente
Mittels Massenspektroskopie. Reaktor Und
Generatoraktivierung. In preparation.
2. WASCH, R., AND H. VOLLSTADT, Mineralogische
Kennzeichnung und Klassifizierung des Luna
16 Materials. Geophys., Vol. 82, 1973, pp. 445-
453.
3. ROSLER, H. J., W. KRAMER, AND P. BEUGE, Ergeb-
nisse Mineralogischer und Petrochemischer
Untersuchungen am Luna 16 Material. In prep-
aration.
4. BAUTSCH, H. J., A. MESSERSCHMIDT, AND J. VET-
TER, Mineralogie und Kristallographie Lunarer
Kristallite und Gldser. In preparation.
5. BANKWITZ, P., AND E. BANKWITZ, Bruchflachen-
analyse an Luna 16 Material. Geophysik, Vol.
82, 1973, pp. 454-464.
6. BERZOV, L. B., A. M. BORSUK, AND V. I. VINO-
GRADOV, VesSest Luny. Itogi Nauki, Ser. geo-
chim., mineral., petrogr, 1971.
7. STILLER, H., H. VOLLSTADT, AND F. C. WAGNER,
Physical Properties of Rocks and Minerals Un-
der Pressure of 60-100 Kbar; Changes in
Wave Velocity in Rocks and Dynamically
Stressed Regions. Paper for the IASPEI Con-
ference about "Earthquake Prediction", Tash-
kent, 1974. In press.
8. MEISSNER, R., Stand der Mondforschung nach
Apollo. Umschau, Vol. 74, No. 3, 1974, pp. 74-
80.


Results of special mechanical analyses of Luna 16 material

Results of special mechanical analyses of Luna 16 material

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server