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1.
George H. Shaw 《Physics of the Earth and Planetary Interiors》1979,20(1):42-47
Calculations of the radial distribution of the energy released in core formation indicate that the cores of all the terrestrial planets may be expected to receive a disproportionate share of the gravitational energy released. Since the model of the process used in these calculations favors transfer of energy to the mantle, it is likely that other reasonable models of the process will result in even more energy being deposited in the cores of the early planets. The calculations also show that it is necessary for a certain amount of core phase to separate and accumulate, before the energy released by gravitational settling is sufficient to supply the latent heat of fusion of the core phase. The amount of melting required to reach this point varies according to the total mass of the planet, and mass fraction of core, but is not particularly great (<5% for the Earth to ～ 37% for the Moon). In the case of the Moon, this amount of segregation, although large, amounts to a surface layer about 260 km thick, similar to the proposed depth of early wholesale melting. Core separation in terrestrial planets appears to be a self-sustaining process even for fairly small bodies, provided that a small amount of a dense potential core phase is present. Although it seems likely to occur rapidly (within 106–107 years) even for small (Moon-size) bodies, detailed kinetic models will be necessary to specify the time scale. 相似文献
2.
Although vigorous mantle convection early in the thermal history of the Earth is shown to be capable of removing several times the latent heat content of the core, we are able to construct a thermal evolution model of the Earth in which the core does not solidify. The large amount of energy removed from the model Earth's core by mantle convection is supplied by the internal energy of the core which is assumed to cool from an initial high temperature given by the silicate melting temperature at the core-mantle boundary. For the smaller terrestrial planets, the iron and silicate melting temperatures at the core-mantle boundaries are more comparable than for the Earth, and the cores of these planets may not possess enough internal energy to prevent core solidification by mantle convection. Our models incorporate temperature-dependent mantle viscosity and radiogenic heat sources in the mantle. The Earth models are constrained by the present surface heat flux and mantle viscosity. Internal heat sources produce only about 55% of the Earth model's present surface heat flow. 相似文献
3.
Fractionation between the metal and silicate components of objects in the inner solar system has long been recognized as a necessity in order to explain the observed density variations of the terrestrial planets and the H-group, L-group dichotomy of the ordinary chondrites. This paper discusses the densities of the terrestrial planets in light of current physical and chemical models of processes in the solar nebula. It is shown that the observed density trends in the inner solar system need not be the result of special fractionation processes, and that the densities of the planets may be direct results of simultaneous application of both physical and chemical restraints on the structure of the nebula, most notably the variation of temperature with heliocentric distance. The density of Mercury is easily attributed to accretion at temperatures so high that MgSiO3 is only partially retained but Fe metal is condensed. The densities of the other terrestrial planets are shown to be due to different degrees of retention of S, O and H as FeS, FeO and hydrous silicates produced in chemical equilibrium between condensates and solar-composition gases. It is proposed that Mercury and Venus Have cores of Fe0, Earth has a core of Fe0 containing substantial amounts of FeS, and Mars has a quite small core of FeS with more FeO in its mantle than in Earth's. Geophysical and geochemical consequences of these conclusions are discussed. 相似文献
4.
Summary The gravitational potential energies of Mercury, Venus and Mars have been computed on the basis of density models and compared to that of the Earth. It has been stated that the specific potential energy per unit mass is very close as regards the pair Earth and Venus, as well as the pair Mercury and Mars.Dedicated to the Memory of K. P 相似文献
5.
6.
Robert Tenzer Ismael Foroughi Lars E. Sjöberg Mohammad Bagherbandi Christian Hirt Martin Pitoňák 《Surveys in Geophysics》2018,39(3):313-335
In planetary sciences, the geodetic (geometric) heights defined with respect to the reference surface (the sphere or the ellipsoid) or with respect to the center of the planet/moon are typically used for mapping topographic surface, compilation of global topographic models, detailed mapping of potential landing sites, and other space science and engineering purposes. Nevertheless, certain applications, such as studies of gravity-driven mass movements, require the physical heights to be defined with respect to the equipotential surface. Taking the analogy with terrestrial height systems, the realization of height systems for telluric planets and moons could be done by means of defining the orthometric and geoidal heights. In this case, however, the definition of the orthometric heights in principle differs. Whereas the terrestrial geoid is described as an equipotential surface that best approximates the mean sea level, such a definition for planets/moons is irrelevant in the absence of (liquid) global oceans. A more natural choice for planets and moons is to adopt the geoidal equipotential surface that closely approximates the geometric reference surface (the sphere or the ellipsoid). In this study, we address these aspects by proposing a more accurate approach for defining the orthometric heights for telluric planets and moons from available topographic and gravity models, while adopting the average crustal density in the absence of reliable crustal density models. In particular, we discuss a proper treatment of topographic masses in the context of gravimetric geoid determination. In numerical studies, we investigate differences between the geodetic and orthometric heights, represented by the geoidal heights, on Mercury, Venus, Mars, and Moon. Our results reveal that these differences are significant. The geoidal heights on Mercury vary from ? 132 to 166 m. On Venus, the geoidal heights are between ? 51 and 137 m with maxima on this planet at Atla Regio and Beta Regio. The largest geoid undulations between ? 747 and 1685 m were found on Mars, with the extreme positive geoidal heights under Olympus Mons in Tharsis region. Large variations in the geoidal geometry are also confirmed on the Moon, with the geoidal heights ranging from ? 298 to 461 m. For comparison, the terrestrial geoid undulations are mostly within ± 100 m. We also demonstrate that a commonly used method for computing the geoidal heights that disregards the differences between the gravity field outside and inside topographic masses yields relatively large errors. According to our estimates, these errors are ? 0.3/+ 3.4 m for Mercury, 0.0/+ 13.3 m for Venus, ? 1.4/+ 125.6 m for Mars, and ? 5.6/+ 45.2 m for the Moon. 相似文献
7.
I. N. Tikhonov 《Journal of Volcanology and Seismology》2010,4(3):213-221
We report the results from a search for statistically significant (at a significance level of <0.05) periodicities that synchronize
the occurrence of large shallow (h ≤ 100 km) earthquakes in the eight world regions with the highest level of seismicity. The periodicities in question include
the synodic periods of planets of the solar system (Mercury, Venus, Mars, and Jupiter), as well as the precession period of
the lunar orbit. In five of the eight regions we have found statistically significant results for the period T ≈ 780 days, corresponding to the synodic period of Mars. The lunar cycle and the period of Mercury were significant in two
regions. These results cannot be accounted for by invoking the disturbing influence of gravitational and tidal forces due
to planets other than the Earth. The significant periodicities were used to develop a forecast (for the period 2004–2009)
of the most probable time intervals for the occurrence of large earthquakes in four regions: Kamchatka, the South Kurils,
northeastern Japan, and the Nankai trough. 相似文献
8.
Hannu Savijärvi 《Surveys in Geophysics》1994,15(6):755-773
The thermodynamics, dynamics, weather and general circulation (climate) of the atmospheres of Venus, Earth and Mars is reviewed, in the light of present knowledge. These three terrestrial planets each have a gaseous sunlit envelope, but the realizations of motions in them are quite different. This makes comparisons of their meteorology very interesting and challenging. 相似文献
9.
无论在行星大小、质量还是轨道速度等方面,金星都是太阳系中与地球最相似的行星.自1960年代初期开始,金星一直是人类深空探测的重要目标.本文简要地回顾了人类探索金星的历史,总结了对金星已有的认识,梳理了金星的主要科学问题,最后介绍了未来的国际探测计划,并建议了我国的金星探测目标.早期对金星的探测以苏联的金星计划(Венера)和美国的水手系列(Mariner)为代表,后期的探测器以欧盟、日本等国家的“金星快车(Venus Express)”、“拂晓号(Akatsuki)”为代表.这些探测结果为我们认识金星大气成分、地表地形和内部结构提供了重要的数据.金星的大气组成以CO2为主,含少量N2,与现在地球的大气组成显著不同,类似早期地球的大气组成.虽然金星地表目前没有液态水,但部分理论模拟工作表明金星地表可能曾经有液态水.一系列探测器对金星地表成分的分析表明,金星地表主要由玄武岩组成.在地形地貌方面,由于金星特殊的地表环境,金星表面风化作用对地表地貌影响很小.金星的地表主要受控于比较年轻的火山作用,发育了许多不同于地球的地貌特征,主要包括区域平原、盾状火山平原、冕状地形以及瓦片状地形等,其动力学机制可能是地幔柱—岩石圈相互作用或地幔对流,至今未发现与板块构造相关的地貌.现阶段金星没有太多大型的、活跃的火山热点,虽然无法估测准确的火山活动速率,但相比地球来说火山活动速率小很多.在内部结构方面,金星具有与地球类似的核幔壳结构.金星的内部组成也与地球类似,例如金星地幔很可能是与地球相似的橄榄岩成分.不存在内部磁场和缺乏板块构造是金星区别于地球的两个重要特征.关于金星为什么没有自身磁场,主流观点是金星地核缺乏对流,无法演化出磁场.而针对金星为什么没有演化出板块构造,目前认为主要有三个可能的原因:地表温度过高,没有软流圈,金星缺乏液态水,其中液态水的缺乏接受度最广.从大气组成、地表岩石组合、构造作用等角度来看,金星都与早期地球非常相似,是我们理解类地行星演化的天然实验室.研究金星和地球为什么会朝不同方向演化,是深入理解包括系外行星在内的行星的宜居性形成与演变的重要途径。因此,金星一直是优先级别最高的深空探测目标之一.近几年,美国、俄罗斯以及欧洲等国家和地区分别针对金星目前主要的科学问题,例如金星是否存在早期海洋、金星的宜居性以及结构和重力场等,先后提出各自的金星探测计划.我国在新的国际竞争中应该、也必然有所作为. 相似文献
10.
The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth. 相似文献
11.
G. H. A. Cole 《Surveys in Geophysics》1986,8(4):439-457
The study of the cosmic chemical abundance of the elements suggests that water (which is a combination of the first and second most abundant chemically active elements) is likely to be the most abundant chemical compound in the solar system.It is found that water indeed appears to be a common constituent of planetary bodies even though its presence is not always directly detectable. The amount involved, and the form it takes, varies from one object to another. The Earth has surface liquid water and crustal hydrate materials and only Mars of the terrestrial planets is also likely to have non-atmospheric water and that in frozen form near the surface. The mantles of the icy satellites, and particularly those of Jupiter and Saturn, are the most extended locations of water in the solar system although Uranus and Neptune are likely to have substantial mid-mantle internal water components. Only Mercury and Moon appear to be devoid of water. The smaller bodies such as comets are excluded from the discussion even though they are now known to be composed largely of water-ice. 相似文献
12.
Karen L. Aplin 《Surveys in Geophysics》2006,27(1):63-108
Atmospheric electrification is not a purely terrestrial phenomenon: all Solar System planetary atmospheres become slightly
electrified by cosmic ray ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and Neptune, and it is possible
on Mars, Venus and Titan. Controversy surrounds the role of atmospheric electricity in physical climate processes on Earth;
here, a comparative approach is employed to review the role of electrification in the atmospheres of other planets and their
moons. This paper reviews the theory, and, where available, measurements, of planetary atmospheric electricity which is taken
to include ion production and ion–aerosol interactions. The conditions necessary for a planetary atmospheric electric circuit
similar to Earth’s, and the likelihood of meeting these conditions in other planetary atmospheres, are briefly discussed.
Atmospheric electrification could be important throughout the solar system, particularly at the outer planets which receive
little solar radiation, increasing the relative significance of electrical forces. Nucleation onto atmospheric ions has been
predicted to affect the evolution and lifetime of haze layers on Titan, Neptune and Triton. Atmospheric electrical processes
on Titan, before the arrival of the Huygens probe, are summarised. For planets closer to Earth, heating from solar radiation
dominates atmospheric circulations. However, Mars may have a global circuit analogous to the terrestrial model, but based
on electrical discharges from dust storms. There is an increasing need for direct measurements of planetary atmospheric electrification,
in particular on Mars, to assess the risk for future unmanned and manned missions. Theoretical understanding could be increased
by cross-disciplinary work to modify and update models and parameterisations initially developed for a specific atmosphere,
to make them more broadly applicable to other planetary atmospheres. 相似文献
13.
《Physics of the Earth and Planetary Interiors》1999,110(1-2):83-93
Using density–pressure relationships for mantle silicate and core alloy closely matching PREM we have constructed six models of the Earth in different evolutionary states. Gravitational energies and elastic strain energies are calculated for models with homogeneous composition, separated mantle and liquid core, separated inner and outer cores with the inner core either liquid or solid and models with increased densities, representing cooling of either the mantle or core. In this way we have isolated the gravitational energy released by each of several evolutionary processes and subtracted the consequent increase in strain energy to obtain the net energy released as heat or geodynamo power. Radiogenic heat (∼7.8×1030 J) is found to contribute only about 25% of the total heat budget, the balance originating as residual gravitational energy from the original accretion and from core separation (14×1030 J). The total energy of compositional convection, driven by inner core formation, is 3.68×1028 J and this is the most important (or even the only) energy source for the dynamo for the most recent 2 billion years. It appears unlikely that the inner core existed much before that time. The total net (gravitational minus strain) energy released in the core by the process of inner core formation, 11.92×1028 J, is not much less than the thermal energy released in this process, 15.1×1028 J. In the mantle the net (gravitational minus strain) energy released by thermal contraction is about 20% of the heat release. All of the numerical results are presented in a manner that allows simple rescaling to any revised density estimates. 相似文献
14.
Since 1969, seismology has been extended beyond the Earth, and seismic sensors have been placed on the surface of other bodies of the solar system. A Lunar seismic network thus operated for the 8 years after 1969, with up to 4 stations, and detected some 1000 Moonquakes per year. A single seismic station was also operated on the Martian surface for 19 months since 1977. Unfortunately, it did not detect any Marsquakes, but produced useful information for future experiments. Remotesensing seismic experiments using Doppler shift observation have also been applied to Jupiter in the last two years and are beginning to return information on the normal modes. Planetary seismology is thus now well developed, and will provide increasing information on the structure and dynamics of the planets and bodies of the solar system. In this paper we review the state of the art in planetary seismology. For the terrestrial planets, we compare the seismic sources, structure and experiments on Earth, Moon and Mars. Such a comparison is useful in evaluating the design of past or future experiments. Results in the seismology of giant planets are also reviewed, stressing the connection between methods and theory. 相似文献
15.
S. V. Starchenko 《Geomagnetism and Aeronomy》2013,53(2):243-246
The typical scales, velocities, and magnetic fields in the liquid core of the Earth are determined by using the analysis results of the magnitude of energy that is available for the geodynamo, physical regularities, and observational data. In this work, it is justified that the geomagnetic field is mainly generated in a regime where the magnetic Lorentz force is equilibrated by the Archimedean buoyancy force and by the Coriolis rotational force and the force of inertia is considerably less than these forces. The characteristic periods obtained in the course of this justification permit one to clarify not only the physical nature of secular geomagnetic variations but also that of jerks. In another regime, which is less probable for the present-day Earth, the main balance of forces is determined by inertia and buoyancy; the magnetic field has no significant effect on the typical rate and scale of convection. This regime seems to be probable in the liquid core of the Earth during inversions or digressions, as well as in depths of Mercury, Mars, Uranus, and Neptune. 相似文献
16.
We present a broad-based review of the observational evidence that pertains to or otherwise implies solid-state convection to be occurring (or have occurred) in the interiors of the terrestrial planets.For the Earth, the motion of the plates is prima facie evidence of large-scale mantle convection. Provided we understand upper-mantle thermal conductivity correctly, heat flow beneath the old ocean basins may be too high to be transported conductively from the upper mantle through the base of the lithosphere and therefore convection on a second smaller scale might be operative. The horizontal scale of plate dimensions implies, due to typical cell aspect ratios observed in convection, that the motion extends to the core-mantle boundary. Improved global data coverage and viscoelastic modeling of isostatic rebound due to Pleistocene deglaciation imply a uniform mantle viscosity, and thus indicate that whole-mantle convection could exist. Additionally, there is some seismic evidence of lithospheric penetration to depths deeper than 700 km. We discuss some salient features and assumption boundedness of arguments for convection confined to the upper mantle and for convection which acts throughout the mantle since the vertical length scale has a profound effect upon the relevance of geophysical observations. The horizontal form of mantle convection may be fully three-dimensional with complex planform and, therefore, searching for correlative gravity patterns in the ocean basins may not be useful without additional geophysical constraints. Many long-wavelength gravity anomalies may arise from beneath the lithosphere and must be supported dynamically, although thermal convection is not a unique explanation. Topography is an additional geophysical constraint, but for wavelengths greater than a few hundred kilometers, a general lack of correlation exists between oceanic residual gravity and topography, except at specific locations such as Hawaii. Theoretical calculations predict a complex relationship between these two observational types. Oceanic gravity data alone shows no regular planform and there is no correlation with any small-scale convective pattern predicted by laboratory experiments.All of the observational evidence argues against Martian plate tectonics occurring now or over much of the history of this planet, but lack of plate tectonics is not an argument against interior convection. The Tharsis uplift on Mars may have resulted from convective processes in the mantle, and the present-day gravity anomaly associated with Tharsis must be supported by the finite strength of the lithosphere or by mantle convection. Stresses imparted by the present topographic load would be greater than a kilobar, in excess of long-term finite strength. Observed fracture patterns are probably a direct result of this load, and the key question concerns the level of resultant strain relief. The global topographic and geomorphic dichotomy between the northern and southern hemisphere required a solid-state flow process to create the accompanying center-of-figure to center-of-mass offset.Lunar heat flow values, in analogy with oceanic heat flow on the Earth, strongly imply a convective mechanism of heat transport in the interior which, based on seismic Q values, is limited to the lower mantle. The presence of moonquakes in this region does not preclude solid-state convective processes. Lunar conductivity profiles provide no information on convection because of the difficulty in conductivity modeling, uniqueness of models, and the uncertainty in the conductivity-temperature relationship. The excess oblateness of the lunar figure over the hydrostatic value does not require convective support; in fact, such a mechanism is unlikely.The presence of a dipole magnetic field on Mercury does not provide a constraint on mantle convection unless its existence can be inextricably linked to a molten core. The non-hydrostatic shape of the equatorial figure, required for the observed resonance between Mercury's rotational and orbital periods, is most likely related to surface processes, as opposed to convection. The resonance implies escape from a 2n resonance and, therefore, is related to the question of a molten core. Further dynamical data is needed to constrain interior models.Interpretation of limited radar imagery for the surface of Venus is enigmatic in terms of plate tectonics and therefore interior convection. Linear tensional and possibly compressional features are observed, but there are also crustal regions which appear to show large impact structures and are thus geologically old and may not have been recycled. 相似文献
17.
S. V. Starchenko 《Izvestiya Physics of the Solid Earth》2017,53(6):908-921
A hydromagnetic dynamo is only possible at a sufficiently powerful convection. In the Earth’s core, it is probably the nonthermal convection very much in excess of its critical level with the molecular transporr coefficients. However, in the case of medium- or large-scale fields, the critical energy level caused by the turbulent tranport coefficients is likely to be slightly below the actual level. This probably explains both the 22-year success of this type of simplified geodynamo models and the energy scaling laws for hydromagnetic fields, which generalize these models. Also the review of energy-dependent analytical and observational estimates of vortex fields, hydromagnetic scale sizes, and velocities in the core is presented. These typical parameters are partly in a new way linked to the observed and more ancient magnetic variations. New, albeit, simplified and self-evident, substantiation is given to the paleomagnetic hypothesis about the predominance of the axial dipole under a certain time averaging. In (Pozzo et al., 2012) and more recent works, it is shown that the adiabatic heat flow and electrical conductivity in the Earth’s core are severalfold higher than the generally accepted estimates. Here, the dynamo supporting Braginsky’s convection (Braginsky, 1963) (under the crystallization of the heavy fraction of a liquid onto the solid core) started less than 1 Ga ago, whereas the more ancient geodynamo was supported by the compositional convection of another type. The known mechanisms implementing this convection, which differ by the scenarios of magnetic evolution, are reviewed. This may help identify the sought mechanism through the most ancient paleomagnetic estimates of the field’s intensity and through the numerical models. The probable mechanisms of generation and their absence for the primordial and recent magnetic field of the studied terrestrial planets are discussed. 相似文献
18.
Recognition that the cooling of the core is accomplished by conduction of heat into a thermal boundary layer (D″) at the base of the mantle, partly decouples calculations of the thermal histories of the core and mantle. Both are controlled by the temperature-dependent rheology of the mantle, but in different ways. Thermal parameters of the Earth are more tightly constrained than hitherto by demanding that they satisfy both core and mantle histories. We require evolution from an early state, in which the temperatures of the top of the core and the base of the mantle were both very close to the mantle solidus, to the present state in which a temperature increment, estimated to be ～ 800 K, has developed across D″. The thermal history is not very dependent upon the assumption of Newtonian or non-Newtonian mantle rheology. The thermal boundary layer at the base of the mantle (i.e., D″) developed within the first few hundred million years and the temperature increment across it is still increasing slowly. In our preferred model the present temperature at the top of the core is 3800 K and the mantle temperature, extrapolated to the core boundary without the thermal boundary layer, is 3000 K. The mantle solidus is 3860 K. These temperatures could be varied within quite wide limits without seriously affecting our conclusions. Core gravitational energy release is found to have been remarkably constant at ～ 3 × 1011 W. nearly 20% of the core heat flux, for the past 3 × 109 y, although the total terrestrial heat flux has decreased by a factor of 2 or 3 in that time. This gravitational energy can power the “chemical” dynamo in spite of a core heat flux that is less than that required by conduction down an adiabatic gradient in the outer core; part of the gravitational energy is used to redistribute the excess heat back into the core, leaving 1.8 × 1011 W to drive the dynamo. At no time was the dynamo thermally driven and the present radioactive heating in the core is negligibly small. The dynamo can persist indefinitely into the future; available power 1010 y from now is estimated to be 0.3 × 1011 W if linear mantle rheology is assumed or more if mantle rheology is non-linear. The assumption that the gravitational constant decreases with time imposes an implausible rate of decrease in dynamo energy. With conventional thermodynamics it also requires radiogenic heating of the mantle considerably in excess of the likely content of radioactive elements. 相似文献
19.
SmNd isotopic data for mineral separates from the ferroan anorthosite 60025 define a precise isochron of 4.44 ± 0.02Ga age. This age is roughly 110 m.y. younger than the formation of the first large solid objects in the solar nebula, as recorded by the radiometric ages of the differentiated meteorites. In the magma ocean model for early lunar differentiation, ferroan anorthosites are the first crustal rocks to form on the Moon. If the Moon is as old as the oldest meteorites, the relatively young age determined for 60025 implies either that the magma ocean did not form synchronously with lunar formation, or that the magma ocean required over 100 m.y. before reaching the stage of ferroan anorthosite crystallization. Alternatively, we propose that the accumulated body of radiogenic isotope data for lunar rocks permit the Moon to be as young as 4.44–4.51 Ga. If so, isotopic evidence for chemical differentiation on the Earth at about this same time suggests that the formation of the Moon is reflected in the chemical evolution of the Earth. This, in turn, is consistent with the idea that the materials that now make up the Moon were derived from the Earth, perhaps ejected by collision between the Earth and another very large planetesimal during the final stages of accumulation of the terrestrial planets. Terrestrial origin models for the Moon lessen the requirement that the Earth and Moon each have near chondritic relative abundances of the refractory elements and could require that certain chemical and isotopic characteristics of both bodies be considered in the framework of the chemical mass-balance of the combined Earth-Moon system. 相似文献
20.
Angioletta Coradini Costanzo Federico Pasquale Lanciano 《Physics of the Earth and Planetary Interiors》1983,31(2):145-160
The extent of formation heating for the Earth and Mars has been evaluated assuming that the terrestrial planets accumulated from planetesimals. The main result is that, even if a long accumulation time is assumed (τ ≥ 100 Ma), it is possible to obtain a planetary structure with a large melted shell taking into account the role played by massive projectiles, which, upon reaching depths of several kilometres, are able to deposit heat significantly below the planetary surface. Internal temperatures, sufficient for the downward migration of the liquid iron alloy, have been obtained. 相似文献