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Oxidation state of iron and cation distribution over M1 and M2 sites in clinopyroxenes from Apollo 12 by Mossbauer absorption spectroscopy, noting cooling history
Clinopyroxene crystallization histories of Apollo 12 porphyritic basalt rocks 12021 and 12052 from Oceanus Procellarum
Size distribution, composition and history of regolith fines at Apollo 12 site
Lunar surface history model, discussing mascons, chemical composition, isochron ages and seismic and electrical properties of samples
Apollo 11 and 12 lunar samples history of irradiation exposure to galactic cosmic rays and solar wind, using rare gas and Gd isotope measurements
Radiation exposure history from fossil tracks in Apollo 12 surface rocks and double core regolith samples, comparing with Saint Severin meteorite
Lunar anorthosite 15415 consists almost entirely of anorthite (homogeneous anorthite 96.6 molecule percent), with accessory diopsidic augite and traces of hypersthene, ilmenite, and a silica mineral. The rock has had a complex metamorphic history. The texture reflects at least two episodes of shearing (followed by intense and partial recrystallization, respectively), one episode of cataclastic deformation, and one or more episodes of shattering and fragmentation.
This paper considers the extent to which Martian craters can be explained by considering asteroidal impact. Sections I, II, and III of this paper derive the diameter distribution of hypothetical asteroidal craters on Mars from recent Palomar-Leiden asteroid statistics and show that the observed Martian craters correspond to a bombardment by roughly 100 times the present number of Mars-crossing asteroids. Section IV discusses the early bombardment history of Mars, based on the capture theory of Opik and probable orbital parameters of early planetesimals. These results show that the visible craters and surface of Mars should not be identified with the initial, accreted surface. A backward extrapolation of the impact rates based on surviving Mars-crossing asteroids can account for the majority of Mars craters over an interval of several aeons, indicating that we see back in time no further than part-way into a period of intense bombardment. An early period of erosion and deposition is thus suggested. Section V presents a comparison with results and terminology of other authors.
The subsolidus cooling history of basaltic rocks can be deduced from the distribution of divalent Mg and Fe ions over the two nonequivalent positions M1 and M2 in pyroxene. The ion exchange reaction between M1 and M2 is generally characterized by rapid kinetics. It is found that the normal cooling process of basalt 14053 was interrupted at a temperature below 840 C and that the rock was then quenched extremely rapidly.
The thermal history of the lunar interior has been investigated for many sets of parameters and initial conditions by the construction of mathematical models. These models have been extended to include the effects of melting and redistribution of radioactive heat sources with time. The models considered include the possibility of heat transfer by lattice conduction, radiative transfer, removal of radioactive heat sources and, in a molten zone, fluid convection. The energy sources are divided into initial temperature sources that operate during the formation of the moon or shortly thereafter, and long-lived radioactive heat sources.
New information is used to demonstrate that better models for the thermal history of the moon are required. As a first step, account is taken of (1) a nonuniform initial composition in terms of fraction of low melting to high melting phase present, and for variation in the uranium, potassium, and thorium contents as a function of depth, (2) partitioning of the radioactive elements between the melt and the solid phases, and (3) a cutoff value of melt which must be exceeded before magma can move to the surface. The results of several attempts to determine whether reasonable conditions, composition, and thermal properties can be expected to give rise to two separate periods of volcanism are discussed. Two models with somewhat different distributions of radioactive heat sources and different conductivities are examined.
The testimony which the main features of the lunar surface bear on the cosmic environment in which the satellite acquired its principal morphological characteristics is examined. It is assumed as a working hypothesis that, in the earliest stages of the moon's history, the lunar sculpture in the continental areas was predominantly shaped by external impacts. It is considered that the argument against heliocentric orbits of particles whose collisions with the moon disfigured most of its continental areas continues to hold good. The distribution of craters due to oblique impacts appears to be essentially at random all over the lunar surface.
The Mintz-Arakawa 2-level general circulation model has been used in a series of experiments to compute the response of the model atmosphere to: (1) a positive sea surface temperature anomaly in the North Pacific Ocean in summer and in winter, (2) an identical anomaly in the South Pacific Ocean in the Southern Hemisphere winter, and (3) anomalous northward and southward displacements of the Northern Hemisphere snow line over the continents. In each case computations were carried out for 90 forecast days. Results are shown in terms of the differences between anomaly and control histories. Time series of certain regional response indices, including area-average sea level pressure and 600 mb circulation indices, as well as 30-day mean sea level pressure maps are used in the analysis. Of particular interest is the evidence of significant interhemisphere influence.
An analytical rationale for the sensitivity-insensitivity of dispersion-strengthened systems to process history is provided. In particular, the research was focussed upon the influence of the particle-matrix interface bond in TD-Nickel and TD-Nichrome, and the manner in which the differences in both elastic constants and thermal expansion coefficients between these phases stress this interface when these alloys are subjected to mechanical and thermal loads upon the mechanical properties of these alloys.
In seasonal computations, the Mintz-Arakawa two-level model is found to be sensitive to a minor alteration in the computational program. Effects of the program change on monthly mean sea level pressure fields are small in the first month, but large in the second and third months, although the meteorological histories generated by both the original and modified programs are equally credible. The inherited effects of a transient (one month) sea surface temperature (SST) anomaly on the computed monthly mean sea level pressure fields over a period of a season are about as large in absolute magnitude as those generated in the model by a persistent (seasonal) SST anomaly. The effects of a transient SST anomaly in the North Pacific Ocean on monthly and seasonal temperature and precipitation in the eastern United States may be large enough to produce a change of one or two class intervals in these predicted weather elements. The model-generated precipitation in the equatorial region is also found to be sensitive to the sea surface temperature field in the North Pacific.
The possible thermal history of the moon is investigated by means of theoretical models. The calculations include the effects of melting and time-dependent redistribution of radioactive heat sources. The known constraints can best be satisfied by a model which is characterized by relatively high initial temperatures close to the melting range; melting and, consequently, fractionation and redistribution of radionuclides would occur during the first 1.5 b.y. and would then be followed by an effective cooling process. Heat flow measurements on the lunar surface should permit a distinction between such a completely fractionated model and a nonfractionated model or a model with restricted fractionation in the outer few hundred kilometers.
Study of the distribution of magnesium and ferrous iron over the M1 and M2 positions in pyroxenes from the basaltic rocks 14053 and 14310, aimed at an analysis of the subsolidus cooling history. The results obtained suggest that the subsolidus cooling of the basalt 14310 occurred at a depth of several meters in a coherent body of appreciable size. As for the 14053, the hot debris of which it was a part were deposited after the projection from the Imbrium basin; some smaller fragments, including 14503, cooled very rapidly in the cold Fra Mauro regolith by conduction.
The lunar velocity profile and laboratory data on terrestrial and lunar rocks are constraints on models of lunar history. They show that shock-induced microcracks are absent from the rocks present in the moon today at depths of 25 to 60 kilometers. All possible causes of this observation are examined, and the most likely explanations are that either the rocks at depths of 25 to 60 kilometers formed after the major impacts ceased or the microcracks have annealed at temperatures of about 600 C over geologically long times.