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1.
harold C. Urey 《Astrophysics and Space Science》1972,16(2):311-323
The problem of the accumulation of the Moon is discussed on the assumption that the Moon is a captured object. If it is such, it is highly improbable that it is the only object of this kind present in the early solar system. Evidence indicating that other massive objects were present at that time is presented. Also, it is pointed out that the interior of the Moon must contain normal solar proportions of the elements of intermediate volatility in the lunar interior, if the Moon accumulated in a gas sphere. 相似文献
2.
The thermal evolution of the Moon as it can be defined by the available data and theoretical calculations is discussed. A wide assortment of geological, geochemical and geophysical data constrain both the present-day temperatures and the thermal history of the lunar interior. On the basis of these data, the Moon is characterized as a differentiated body with a crust, a 1000-km-thick solid mantle (lithosphere) and an interior region (core) which may be partially molten. The presence of a crust indicates extensive melting and differentiation early in the lunar history. The ages of lunar samples define the chronology of igneous activity on the lunar surface. This covers a time span of about 1.5 billion yr, from the origin to about 3.16 billion yr ago. Most theoretical models require extensive melting early in the lunar history, and the outward differentiation of radioactive heat sources.Thermal history calculations, whether based on conductive or convective computation codes define relatively narrow bounds for the present day temperatures in the lunar mantle. In the inner region of the 700 km radius, the temperature limits are wider and are between about 100 and 1600°C at the center of the Moon. This central region could have a partially or totally molten core.The lunar heat flow values (about 30 ergs/cm2s) restrict the present day average uranium abundance to 60 ± 15 ppb (averaged for the whole Moon) with typical ratios of K/U = 2000 and Th/U = 3.5. This is consistent with an achondritic bulk composition for the Moon.The Moon, because of its smaller size, evolved rapidly as compared to the Earth and Mars. The lunar interior is cooling everywhere at the present and the Moon is tectonically inactive while Mars could be and the Earth is definitely active. 相似文献
3.
The unipolar induction mechanism is employed to calculate electric field profiles in the interior of a chemically homogeneous Moon possessing a steep radial thermal gradient characteristic of long-term radioactive heating. The thermal models used are those of Fricker, Reynolds, and Summers. From the magnetic field, the magnetic back pressure upon the solar wind is found. The electric field profile is shown to depend only upon the activation energy,E
o, of the geological material and the radial gradient of the reciprocal temperature. The current is additionally dependent upon the coefficient of the electrical conductivity function but only by a scale factor. Since the Moon is experimentally known to correspond to the case of weak interaction with the solar wind, the magnetic back pressure is calculated without the need for an iterative procedure. The results indicate that a hot Moon can yield sufficient current flow so that the magnetic back pressure is observable as a vestigial limb shock wave using an activation energy of about 2/3 eV together with a conductivity coefficient of about 103 mhos/m. Such matter is approximated by diabase-like composition, although the result that both the activation energy and coefficient enter into the current determination does not rule out the possibility of a match with other similar substances. The calculations are entirely consistent with earlier results which indicated a model where the unipolar current density is dominated by a high impedance surface layer and a strong shock wave is inhibited. In addition to the magnetic back pressure, the integration of the current continuity equation permits current densities and joule heating rates to be calculated, though the magnitude of the latter for present solar wind conditions is not thermally important.On leave from NASA Ames Research Center 相似文献
4.
This paper presents a review of research findings on the various forms of water on the Moon. First, this is the water of the
Moon’s interior, which has been detected by sensitive mass spectrometric analysis of basaltic glasses delivered by the Apollo
15 and Apollo 17 missions. The previous concepts that lunar magmas are completely dehydrated have been disproved. Second,
this is H2O and/or OH in a thin layer (a few upper millimeters) of the lunar regolith, which is likely a result of bombardment of the
oxygen contained in the lunar regolith with solar wind protons. This form of water is highly unstable and quite easily escapes
from the surface, possibly being one of the sources of the water ice reservoirs at the Moon’s poles. Third, this is water
ice associated with other frozen gases in cold traps at the lunar poles. Its possible sources are impacts of comets and meteorites,
the release of gas from the Moon’s interior, and solar wind protons. The ice trapped at the lunar polars could be of practical
interest for further exploration of the Moon. 相似文献
5.
A. G. W. Cameron 《Earth, Moon, and Planets》1973,7(3-4):377-383
The basic geochemical model of the structure of the Moon proposed by Anderson, in which the Moon is formed by differentiation of the calcium, aluminium, titanium-rich inclusions in the Allende meteorite, is accepted, and the conditions for formation of this Moon within the solar nebula models of Cameron and Pine are discussed. The basic material condenses while iron remains in the gaseous phase, which places the formation of the Moon slightly inside the orbit of Mercury. Some condensed metallic iron is likely to enter the Moon in this position, and since the Moon is assembled at a very high temperature, it is likely to have been fully molten, so that the iron can remove the iridium from the silicate material and carry it down to form a small core. Interactions between the Moon and Mercury lead to the present rather eccentric Mercury orbit and to a much more eccentric orbit for the Moon, reaching past the orbit of the Earth, establishing conditions which are necessary for capture of the Moon by the Earth. In this orbit the Moon, no longer fully molten, will sweep up additional material containing iron oxide. This history accounts in principle for the two major ways in which the bulk composition of the Moon differs from that of the Allende inclusions.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973. 相似文献
6.
Shailendra Kumar 《Icarus》1976,28(4):579-591
Measurements made during the Mariner 10 flybys of Mercury have shown that this planet has a tenuous atmosphere, somewhat similar to that of the Moon, which consists of at least helium and can be classified as an exosphere. The amount of helium observed can be supplied by either the accretion of only a fraction of the solar wind He2+ diffusing across the magnetopause, or from outgassing of radiogenic helium from the planetary crust. The role of solar wind in the maintenance and depletion of Mercury's atmosphere is discussed in view of the density upper limits established from Mariner 10. The argon supply rate on Mercury is probably not more than that on the Earth, but it is difficult to say whether Mercury is deficient in potassium or not on the basis of the present data. The global outgassing of CO2 and H2O from the planet interior is estimated to be at least four orders of magnitude smaller than for Earth which indicates that either Mercury is deficient in volatiles or that this planet is very inactive. 相似文献
7.
Paul J. Coleman Jr. G. Schubert C. T. Russell L. R. Sharp 《Earth, Moon, and Planets》1972,4(3-4):419-429
A preliminary analysis of the data from the UCLA magnetometer on board the Apollo 15 subsatellite indicates that remnant magnetization is a characteristic property of the Moon, that its distribution is such as to produce a rather complex pattern or fine structure, and that a detailed mapping of its distribution is feasible with the present experiment. The analysis also shows that lunar induction fields produced by transients in the interplanetary magnetic field are detectable at the satellite orbit so that in principle the magnetometer data can be used to determine the latitudinal and longitudinal as well as radial dependences of the distribution of electrical conductivity within the Moon. Finally, the analysis indicates that the plasma void or diamagnetic cavity which forms behind the Moon when the Moon is in the solar wind, is detectable at the satellite's orbit and that the flow of the solar wind near the limbs is usually rather strongly disturbed.Publication No. 981. Institute of Geophysics and Planetary Physics. 相似文献
8.
Jafar Arkani-Hamed 《Earth, Moon, and Planets》1973,6(1-2):100-111
Using data from the present gravitational potential and surface topography of the Moon, it is possible to determine a lower
limit of about 5 b.y. for the relaxation time of the mascons. Assuming that the Moon has behaved as a Maxwellian viscoelastic
body since the formation of the mascons, this relaxation time indicates a value of about 1027 poise for the viscosity of the lunar interior. Such a high viscosity implies that there has been no convection current inside
the upper 800 km of the Moon since the formation of the mascons.
Lunar Science Institute Contribution No. 99.
The research in this paper was done while the author was a Visiting Scientist at the Lunar Science Institute, which is operated
by the Universities Space Research Association under Contract No. NSR 09-051-001 with the National Aeronautics and Space Administration. 相似文献
9.
10.
Mark J. Reid 《Icarus》1973,20(2):240-248
Tidal interactions, by altering spin and orbital parameters, can lead to the destruction of bodies in the solar system. Specifically, tidal interactions can rapidly decay the orbit of an object which revolves around a satellite. Hence, almost any object which once orbited a satellite would have impacted the satellite early in the history of the solar system. This may explain the absence of such objects today.The tidal loss of lunar-orbiting objects offers a solution to the problem of how objects may have been “stored” for ≈0.5 eons prior to impacting the Moon. The craters produced by the impacts of lunar-orbiting objects should have characteristic sizes, shapes, and ages. The Crisium and Serenitatis basins exhibit these characteristics, and, therefore, could have been produced by the impact of a lunar orbiting object. Finally, the possibility that the Imbrium and Crisium basins originated from one object, which fragmented prior to impact, is discussed. 相似文献
11.
Mahesh Anand 《Earth, Moon, and Planets》2010,107(1):65-73
One of the most exciting recent developments in the field of lunar science has been the unambiguous detection of water (either
as OH or H2O) or water ice on the Moon through instruments flown on a number of orbiting spacecraft missions. At the same time, continued
laboratory-based investigations of returned lunar samples by Apollo missions using high-precision, low-detection, analytical
instruments have for the first time, provided the absolute abundance of water (present mostly as structurally bound OH− in mineral phases) in lunar samples. These new results suggest that the Moon is not an anhydrous body, questioning conventional
wisdom, and indicating the possibility of a wet lunar interior and the presence of distinct reservoirs of water on the lunar
surface. However, not all recent results point to a wet Moon and it appears that the distribution of water on the Moon may
be highly heterogeneous. Additionally, a number of sources are likely to have contributed to the water inventory of the Moon
ranging from primordial water to meteorite-derived water ice through to the water formed during the reaction of solar-wind
hydrogen with the lunar soil. Water on the Moon has implications for future astrobiological investigations as well as for
generating resources in situ during future exploration of the Moon and other airless bodies in the Solar System. 相似文献
12.
Don L. Anderson 《Earth, Moon, and Planets》1973,8(1-2):33-57
The accretion during condensation mechanism, if it occurs during the early over-luminous stage of the Sun, can explain the differences in composition of the terrestrial planets and the Moon. An important factor is the variation of pressure and temperature with distance from the Sun, and in the case of the Moon and captured satellites of other planets, with distance from the median plane. Current estimates of the temperature and pressure in the solar nebula suggest that condensation will not be complete in the vicinity of the terrestrial planets, and that depending on location, iron, magnesium silicates and the volatiles will be at least partially held in the gaseous phase and subject to separation from the dust by solar wind and magnetic effects associated with the transfer of angular momentum just before the Sun joins the Main Sequence.Many of the properties of the Moon, including the enrichment in Ca, Al, Ti, U, Th, Ba, Sr and the REE and the depletion in Fe, Rb, K, Na and other volatiles can be understood if the Moon represents a high temperature condensate from the solar nebula. Thermodynamic calculations show that Ca, Al and Ti rich compounds condense first in a cooling nebula. The high temperature mineralogy is gehlenite, spinel, perovskite, Ca-Al-rich pyroxenes and anorthite. The model is consistent with extensive early melting, shallow melting at 3 AE and with presently high deep internal temperatures. It is predicted that the outer 250 km is rich in plagioclase and FeO. The low iron content of the interior in this model raises the interior temperatures estimated from electrical conductivity by some 800°C. The lunar crust is 80% gabbroic anorthosite, 20% basalt and is about 250-270 km thick. The lunar mantle is probably composed of spinel, merwinite and diopside with a density of 3.4 g cm–3.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973.Contribution No. 2260, Division of Geological and Planetary Sciences California Institute of Technology, Pasadena, Calif. 91109, U.S.A. Presented at theIAU Symp. Cosmochem., Cambridge, Mass. August 14-16, 1972. 相似文献
13.
A three-dimensional hybrid code is used to study the electromagnetic disturbances in the solar wind that arise due to the absorption effect of the Moon. Due to the nearly insulating nature of the Moon, interplanetary magnetic fields (IMFs) can move through the interior without hindrance. However, the near-vacuum created in the wake region due to the lunar absorption effect will lead to enhancement of the strength of the magnetic field by a factor of about 1.4 in the middle of the lunar wake and lead to depletions at two sides. The situations arising from different orientations of the interplanetary magnetic fields relative to the radial direction are compared. Asymmetries of the inward diffusions both along and perpendicular to the field lines are also observed. The electric field formed from the plasma convection could reach a magnitude of 0.2–0.8 mV/m at the border of the wake. The role of the electric field on the inward accelerations is important to the geometry of the lunar wake. 相似文献
14.
The electrical conductivity of olivine and pyroxene is a strong function of the fugacity of oxygen in the atmosphere with which the mineral is in equilibrium. Lunar temperature profiles calculated from data on the electrical conductivity of these two minerals at oxygen fugacities similar to those which exist in the Moon indicate considerably higher temperatures for the lunar interior than obtained from conductivity data collected under normal atmospheric conditions. These high interior temperatures, the extensive differentiation associated with the formation of the lunar maria, and the radioactive element content of the Moon indicate that the Moon accreted at temperatures between 600 and 1000°C. Gravitational heating during accretion would lead to melting of at least the outer 200 km of the Moon and would produce conditions favourable to separation of a metal-sulfide melt sufficient to form a core of 200–300 km radius. Such a core would reach the center of the Moon within a few million years after accretion. This core could produce the remanent magnetization observed in the surface rocks. Dynamo action would cease with the cessation of convective motion within the core as the temperature of the surrounding mantle increased due to radioactive heating. With the radioactivity assumed in the present model and the high accretion temperature, this event would require less than 2 b.y., but more than 1.6 b.y.Paper dedicated to Professor Harold C. Urey on the occasion of his 80th birthday on 29 April 1973. 相似文献
15.
A simple analytical model is developed from which we have calculated the temperature throughout the lunar interior resulting
from internal heat sources and the imposition of surface temperature boundary conditions. The surface temperature is determined
almost entirely by the balance of solar heating and surface reradiation; as a consequence this temperature is latitude dependent,
decreasing towards the lunar poles. The internal solution shows that the latitude effect exists almost undiminished to great
depths within the Moon.
It is suggested that this dependence on latitude may have a significant effect on the Moon’s thermal evolution. Using the
liquefaction model the high concentration of lunar maria at low latitudes may be explained. 相似文献
16.
Defining the solar brightness temperature accurately at millimeter wavelengths has always been challenging. One of the main reasons has been the lack of a proper calibration source. New Moon was used earlier as a calibration source. We carried out a new extensive set of observations at 8 mm using the New Moon for calibration. The solar and Moon observations were made using the 14-meter radiotelescope operated by the Aalto University Metsähovi Radio Observatory in Finland. In this article, we present our method for defining the brightness temperature of the quiet-Sun level (QSL). Based on these observations, we found \(8100~\mbox{K} \pm 300~\mbox{K}\) to be the mean value for the QSL temperature. This value is between the values that were reported in earlier studies. 相似文献
17.
It is generally accepted that the Earth-Moon separation is at present increasing due to tidal dissipation. Values for the corresponding lunar deceleration and the related slowing of the Earth's rotation are obtained from astronomical observations and by studies of ancient eclipses. Extrapolation of these values leads to a close approach of the Earth and Moon 1–3 b.y. BP. However, justification for such an extrapolation is required. It has been hypothesized that periodicities in the Precambrian stromatolites can be used to determine the number of solar days in a lunar month prior to 500 m.y. BP. These data combined with dynamic constraints on the number of solar days in a lunar month indicate a close approach of the Earth and Moon at 2.85 ± 0.25 b.y. BP. It is suggested that the mare volcanism on the Moon and high-temperature Archean volcanism on the Earth prior to this date were caused by tidal heating. It is also suggested that the strong tidal heating during a close approach could have contributed to the formation of the first living organisms. 相似文献
18.
A method for investigating the brightness distribution near the solar limb at millimeter wavelengths
The brightness distribution near the solar limb has been investigated by means of a technique in which derivatives of drift scans of the Sun were compared with derivatives of drift scans of the Moon. The results obtained at 88.3 GHz (3.4 mm) indicate that the Sun is limb neutral within the uncertainty of our measurement. If limb brightening or darkening is present, it represents less than 1.6 % or 1.2 %, respectively, of the total power received from the Sun at this wavelength. 相似文献
19.
Surface-correlated noble gases in lunar soils are primarily implanted SW (solar wind) noble gases. However, they also include apparently orphan radiogenic 40Ar, 129Xe, and 244Pu-derived fission Xe in excess of plausible primordial solar origin. These orphan radiogenic components are usually assigned a lunar origin, in a scenario in which radiogenic noble gases produced in the lunar interior were degassed into the transient atmosphere and then re-implanted to the lunar surface together with SW. There are some quantitative difficulties with this scenario, however, and it requires special constraints on the degassing history of the Moon that have not emerged from more general thermal history models. We therefore urge consideration of alternative hypotheses. As a possible source for the orphan radiogenic noble gases, we have examined planetary pollution of the Sun, as suggested by studies of extrasolar planetary systems (e.g., Murray et al., 2001, Astrophys. J. 555, 801-815; Israelian et al., 2001, Nature 411, 163-166). Pollution of the Sun by 2M⊕ (two Earth mass) planetary materials (Murray et al., 2001, Astrophys. J. 555, 801-815) is likely not significant for Ar but could be important to account for orphan Xe in the Moon. 相似文献
20.
During the few days centered about new Moon, the lunar surface is optically hidden from Earth-based observers. However, the Moon still offers an observable: an extended sodium tail. The lunar sodium tail is the escaping “hot” component of a coma-like exosphere of sodium generated by photon-stimulated desorption, solar wind sputtering and meteoroid impact. Neutral sodium atoms escaping lunar gravity experience solar radiation pressure that drives them into the anti-solar direction forming a comet-like tail. During new Moon time, the geometry of the Sun, Moon and Earth is such that the anti-sunward sodium flux is perturbed by the terrestrial gravitational field resulting in its focusing into a dense core that extends beyond the Earth. An all-sky camera situated at the El Leoncito Observatory (CASLEO) in Argentina has been successfully imaging this tail through a sodium filter at each lunation since April 2006. This paper reports on the results of the brightness of the lunar sodium tail spanning 31 lunations between April 2006 and September 2008. Brightness variability trends are compared with both sporadic and shower meteor activity, solar wind proton energy flux and solar near ultra violet (NUV) patterns for possible correlations. Results suggest minimal variability in the brightness of the observed lunar sodium tail, generally uncorrelated with any single source, yet consistent with a multi-year period of minimal solar activity and non-intense meteoric fluxes. 相似文献