The Earth Moon

The Earth s Moon is the fifth largest satellite in the solar system. Its distance from the Earth is only 30 times the diameter of the Earth, the orbit is elliptical. The nearest distance to Earth (perigee) is 363 104 km, the largest distance (apogee) is 405 696 km. The semi major-axis is 384 399 km. The orbital period is 27 d 7 h 43.1 min which exactly corresponds to its rotational period. The orbit of the Moon is inclined to the plane of the ecliptic by about 5.1°. The mean radius of the Moon is 1737.1 km which is 0.273 that of the Earth s radius. The surface area is about 37 X 10 km. The density is relatively high and corresponds more to that of terrestrial planets and is 3.34 gcm . Our Moon is a relatively dark body with a surface albedo of 0.12. 

The Moon is in geosynchronous rotation keeping nearly always the same face towards Earth. In fact because of the so called libration effects, we can see about 59% of its surface from Earth. The side that face towards Earth is called the near side, the other hemisphere is called the far side (sometimes also the dark side however this is not correct since also the far side is illuminated by the sun as is the near side). However, the far side was unknown before it was first photographed by the Soviet probe Luna 3 in 1959. The two sides are different (see Eig. 4.24), the far side is almost completely absent of the big plains that are called maria. 

The lunar terrains are generally divided into bright highlands (terrae) which are heavily cratered and dark plains (maria) where few craters are found. The maria constitute 16% of the lunar surface but as it has been pointed out already, on the 

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Among the oldest rocks on Earth are those on Isua, an island off the coast of Greenland they are 3.8 Gyr old, formed some 0.7 Gyr after accretion of the Earth. The rocks mark the beginning of the Archean period of geological time. The Isua rocks suggest that there was an extensive hydrosphere at this time, with erosion, transportation and deposition of minerals from water solution. The oldest lunar rocks, however, record an earlier high-temperature event - the Earth-Moon capture event. 

The delivery of volatiles to Earth and Mars must have been similar but where has the early Martian atmosphere gone The atmosphere of the inner planets can be seen in Table 7.3. Cometary and meteorite impacts can deliver material to a planet but are also responsible for a process called impact erosion where the atmosphere could be lost due to an impact such as the Earth-Moon capture event. Current estimates suggest that impact erosion may be responsible for the loss of 100 times the current mass of the Martian atmosphere. 

The basic idea in radioactive age-dating of rocks (from the Earth, Moon and meteorites) is to find the ratio of daughter to parent in an isolated system. Thus the age inferred is usually the solidification age which is the time since the last occasion when chemical fractionation was halted by solidification. (K-Ar dating gives a gas-retention age which can be slightly shorter.)... 

The assignment of the earth/moon system to one precursor nebular reservoir, and meteorites to a second, while still logically possible, was shown experimentally to be unnecessary by Thiemens and coworkers (reading list). In the early 1980s these workers studied isotope fractionation during the synthesis of ozone from molecular oxygen in an electric discharge operated at low pressure. The product ozone was... 

Norman M, McCulloch M, O Neill H, Brandon A (2004) Magnesium isotopes in the Earth, Moon, Mars, and Pallasite parent body high precision analysis of olivine by laser ablation multi-collector ICPMS. Lunar and Planetary Science Conference XXXV 1447... 

SNC-meteorites have an average 8 0-value of 4.3%c, which is distinctly lower than the 5.5%c value for the Earth-Moon system (Clayton and Mayeda 1996 Franchi... 

Nd system is used primarily to investigate the nature and timing of accretion of planetary bodies, such as the Earth, Moon, Mars, and Vesta. Current work is aimed at unraveling the roles of nebular and planetary processes in the isotopic systematics of these bodies. 

In this chapter, we review what is known about the chronology of the solar system, based on the radioisotope systems described in Chapter 8. We start by discussing the age of materials that formed the solar system. Short-lived radionuclides also provide information about the galactic environment in which the solar system formed. We then consider how the age of the solar system is estimated from its oldest surviving materials - the refractory inclusions in chondrites. We discuss constraints on the accretion of chondritic asteroids and their subsequent metamorphism and alteration. Next, we discuss the chronology of differentiated asteroids, and of the Earth, Moon, and Mars. Finally, we consider the impact histories of the solar system bodies, the timescales for the transport of meteorites from their parent bodies to the Earth, and the residence time of meteorites on the Earth s surface before they disintegrate due to weathering. 

Given our focus on cosmochemistry, we will consider only chronology based on radiogenic isotopes. Most planetary chronology is presently based on crater counting (discussed briefly in Box 9.1), and only the Earth, Moon, and Mars have provided samples that can be analyzed in the laboratory for radioisotopes. However, these three bodies illustrate what could be learned from samples of other terrestrial planets. 

The applications of activation analysis are almost innumerable. In the physical sciences, activation analysis is used in trace-element analysis of semiconductor materials, metals, meteorites, lunar samples, and terrestrial rocks. In most cases, the multielemental analysis feature of activation analysis is used to measure the concentrations of several trace-elements simultaneously. From these detailed studies of trace-element abundance patterns, one has been able to deduce information about the thermal and chemical history of the Earth, moon, Mars, and meteorites, as well as the source or age of an object. 

A significant aspect of skeletal growth in corals is the existence of an internal calendar where daily, seasonal, and annual records are kept on file in the form of individual or series of bands. The band thicknesses within a species are environmentally controlled. The number of bands per year in fossil corals has been used in studies on the Earth-Moon system, i.e. effect of tidal friction on number of days per year336. ... 

Floran R. J., Caulfield J. B. D., Harlow G. E., and Prinz M. (1978) Impact origin for the Simondium, Pinnaroo, and Hainholz mesosiderites imphcations for impact processes beyond the Earth—Moon system. Proc. Lunar Planet. Sci. Conf. 9, 1083-1114. 

Co-accretion. This theory proposes that the Earth and Moon simply accreted side by side. The difficulty with this model is that it does not explain the angular momentum of the Earth-Moon system, nor the difference in density, nor the difference in volatile depletion (Taylor, 1992). 

Canup R. M. and Agnor C. (1998) Accretion of terrestrial planets and the earth-moon system. In Origin ofthe Earth and Moon, LPI Contribution No. 597 Lunar and Planetary Institute, Houston, pp. 4-7. 

Ringwood A. E. (1990) Earhest history of the Earth-Moon system. In Origin of the Earth (eds. A. E. Newsom and J. H. Jones). Oxford University Press, Oxford, pp. 101-134. 

Miinker C., Pfander J. A., Weyer S., Biichl A., Kleine T., and Mezger K. (2003) Evolution of planetary cores and the earth-moon system from Nb/Ta systematics. Science 30, 84-87. 

Newsom H. and Drake M. J. (1983) Experimental investigations of the partitioning of phosphorus between metal and silicate phases implications for the Earth, Moon and eucrite parent body. Geochim. Cosmochim. Acta 47, 93-100. 

Ohtani E., Yurmoto H., Segawa T., and Kato T. (1995) Element partitioning between MgSi03 perovskite, magma, and molten iron constraints for the earliest processes of the Earth-Moon system. In The Earth s Central Part Its Structure and Dynamics (ed. T. Yukutake). Terra Scientific, Tokyo, Japan, pp. 287-300. 

Although not strictly related to mantle depletion and crust formation, Hf- W isotopic compositions do provide clear evidence for early planetary differentiation of the Earth, Moon, and Mars related to core formation. The results (Kleine et al., 2002 Yin et al., 2002 Schoenberg et al., 2002) from this short half-life t — 8 Myr) system provide convincing evidence that metal... 

Wanke H. and Dreibus G. (1982) Chemical and isotopic evidence for the early history of the Earth—Moon system. In Tidal Friction and the Earth s Rotation (eds. P. Brosche and J. Sundermann). Springer, Berlin, pp. 322—344. 

Jupiter, and Saturn. These planets and the sun also perturb the moon s orbit around the Earth— Moon system s center of mass. The use of mathematical series for the orbital elements as functions of time can accurately describe perturbations of the orbits of solar system bodies for limited time intervals. For longer intervals, the series must be recalculated. 

As accurately as these calculations can be made, however, the behavior of celestial bodies over long periods of time cannot always be determined. For example, the perturbation method has so far been unable to determine the stability either of the orbits of individual bodies or of the solar system as a whole for the estimated age of the solar system. Studies of the evolution of the Earth-Moon system indicate that the Moon s orbit may become unstable, which will make it possible for the Moon to escape into an independent orbit around the Sun. Recent astronomers have also used the theory of chaos to explain irregular orbits. 

The overwhelming majority of filaments are made of NS-W (sag-resistant tungsten). Only for special shock and vibration resistant lamps are W-Th02 or W-Re wires used. Every year, about 20 billion meters of lamp wire are drawn, a length which corresponds to about 50 times the earth-moon distance [7.8]. 

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