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1.
One of the principal scientific reasons for wanting to resume in situ exploration of the lunar surface is to gain access to the record it contains of early Solar System history. Part of this record will pertain to the galactic environment of the Solar System, including variations in the cosmic ray flux, energetic galactic events (e.g., supernovae and/or gamma-ray bursts), and passages of the Solar System through dense interstellar clouds. Much of this record is of astrobiological interest as these processes may have affected the evolution of life on Earth, and perhaps other Solar System bodies. We argue that this galactic record, as for that of more local Solar System processes also of astrobiological interest, will be best preserved in ancient, buried regolith (‘palaeoregolith’) deposits in the lunar near sub-surface. Locating and sampling such deposits will be an important objective of future lunar exploration activities.  相似文献   

2.
A summary is given of the literature data on the content of volatiles in the lunar regolith, the characterization of the likely sources of the volatiles, and the possible processes of their migration and burial. The main sources of volatiles in the regolith are the solar wind, small Solar System bodies (comets and meteorites), and the lunar interior. Different sources are the leading ones for different volatiles. Water and other volatiles can accumulate on the surface and in the near-surface layers of the Moon only in the so-called cold traps in polar basins, where other volatiles, as well as water ice, including highly toxic elements such as mercury and cadmium must be accumulated. The content of volatiles in the lunar interior is comparable to that in terrestrial rocks. Water could have played an important role in the early stages of the Moon’s history, e.g., in the formation of mare basalts. The isotopic composition of the lunar juvenile water is similar to that on the Earth, which suggests a common origin of the terrestrial and lunar water.  相似文献   

3.
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   

4.
Wenzhe Fa 《Icarus》2007,190(1):15-23
3He (helium-3) in the lunar regolith implanted by the solar wind is one of the most valuable resources because of its potential as a fusion fuel. The abundance of 3He in the lunar regolith is related to solar wind flux, lunar surface maturity and TiO2 content, etc. A model of solar wind flux, which takes account of variations due to shielding of the nearside when the Moon is in the Earth's magnetotail, is used to present a global distribution of relative solar wind flux over the lunar surface. Using Clementine UV/VIS multispectral data, the global distribution of lunar surface optical maturity (OMAT) and the TiO2 content in the lunar regolith are calculated. Based on Apollo regolith samples, a linear relation between 3He abundance and normalized solar wind flux, optical maturity, and TiO2 content is presented. To simulate the brightness temperature of the lunar surface, which is the mission of the Chinese Chang-E project's multichannel radiometers, a global distribution of regolith layer thickness is first empirically constructed from lunar digital elevation mapping (DEM). Then an inversion approach is presented to retrieve the global regolith layer thickness. It finally yields the total amount of 3He per unit area in the lunar regolith layer, which is related to the regolith layer thickness, solar wind flux, optical maturity and TiO2 content, etc. The global inventory of 3He is estimated as 6.50×108 kg, where 3.72×108 kg is for the lunar nearside and 2.78×108 kg is for the lunar farside.  相似文献   

5.
Abstract Solar noble gases He, Ne, Ar and Kr implanted in the H3–6 meteorite regolith breccia Acfer 111 agree in their elemental composition with that in present-day solar wind and, except for a 25% deficit of 4He, also with adopted solar abundances. The presence of such unfractionated solar gases makes Acfer 111 unique (until now). Closed system stepped etching releases noble gases that can be explained as mixtures of two distinct types of He, Ne, and Kr of isotopic compositions as they have been derived previously from meteorites and lunar samples that contain heavily fractionated solar gases. Since the same putative end members, ascribed to the solar wind (SW) and supra-thermal solar energetic particles (SEP), are also present in Acfer 111, we argue that these end members represent two truly independent components. We discount the possibility that one isotopic composition derived from the other by diffusion of the gases within, or upon their release from, their host phases. The isotopic signatures of noble gases in Acfer 111 agree with those in a lunar ilmenite of young antiquity ?100 Ma) but are in disagreement with the noble gases in lunar ilmenite 79035 of 1–2 Ga antiquity. Systematic changes are discussed of the nuclide abundance ratios as etching proceeds; they are ascribed to differences in trapping efficiency and in penetration depth of the different noble gas ion species upon their implantation.  相似文献   

6.
Solar System Research - The ionization-type cosmic dust detector METEOR-L is being developed for the lunar orbiter Luna-26 and is designed to study the distribution of meteoric bodies in space by...  相似文献   

7.
For better insight into lunar radio emissions, observations of the Moon were made during the maximal Geminids meteor shower and during the lunar eclipse without external effects. Statistical processing of the obtained data was carried out. It was found that the lunar endogenous and exogenous processes are displayed in both the seismic-emission fields and lunar nonthermal electromagnetic emissions. Both types of signals demonstrate good correlation. The seismic and electromagnetic emission processes have common periodicities, some of which determine the internal structure of the Moon. Similar regularities are expected for other bodies of the Solar System.  相似文献   

8.
Lunar electric fields,surface Potential and Associated Plasma Sheaths   总被引：1，自引：0，他引：1  
This paper reviews the electric field environment of the Moon. Lunar surface electric potentials are reported as follows: Solar Wind - Dayside: øo + 10 to + 18 V Solar Wind - Terminator: øo ç ? 10 to ? 100 V Electron and ion densities in the plasma sheath adjacent to each surface potential regime are evaluated and the corresponding Debye length estimated. The electric fields are then approximated by the surface potential over the Debye length. The results are: Solar Wind - Dayside: Eo ? 10 V m?1 outward Solar Wind - Terminator: Eo ç 1 to 10 V m?1 inward These fields are all at least 3 orders of magnitude higher than the pervasive solar wind electric field; however they are confined to within a few tens of meters of the lunar surface.  相似文献   

9.
Ralph B. Baldwin 《Icarus》1974,23(1):97-107
The bodies which produced the premare impact craters on the moon contained a much higher proportion of smaller bodies in the earliest observable times than subsequently. This suggests that the earth and moon accreted from small objects with only an occasional large planetoid.If the earliest observable lunar craters are 4.3 × 109 yr old, the half-life of the primitive planetesimals which produced the giant lunar craters larger than 161 km in diameter, was 143 × 106 yr, while the half-life of the primitive planetesimals which produced lunar craters larger than 1 km in diameter was only 88 × 106 yr. The half-life of the bodies which produced 1 km craters was still shorter, about 75 × 106 yr.  相似文献   

10.
The solar wind provides a source of solar abundance data that only recently is being fully exploited. The Ion Composition Instrument (ICI) aboard the ISEE-3/ICE spacecraft was in the solar wind continuously from August 1978 to December 1982. The results have allowed us to establish long-term average solar wind abundance values for helium, oxygen, neon, silicon, and iron. The Charge-Energy-Mass (CHEM) instrument aboard the CCE spacecraft of the AMPTE mission has measured the abundance of these elements in the magnetosheath and has also added carbon, nitrogen, magnesium, and sulfur to the list. There is strong evidence that these magnetosheath abundances are representative of the solar wind. Other sources of solar wind abundances are Solar Energetic Particle (SEP) experiments and Apollo lunar foils. When comparing the abundances from all of these sources with photospheric abundances, it is clear that helium is depleted in the solar wind while silicon and iron are enhanced. Solar wind abundances for carbon, nitrogen, oxygen, and neon correlate well with the photospheric values. The incorporation of minor ions into the solar wind appears to depend upon both the ionization times for the elements and the Coulomb drag exerted by the outflowing proton flux.  相似文献   

11.
Micrometeorite bombardment and irradiation by solar wind and cosmic ions cause variations in the optical properties of the small Solar System bodies surface materials. These space weathering processes are reasonably well understood for the Moon and S-type asteroids. The research is based on laboratory experiments performed by several groups on meteorites and minor bodies surface analogues, whose results have been applied to the spectral modeling and interpretation of observations from large surveys and space missions. Recent results from young asteroidal families, and the relation between spectral slopes and dynamical properties, have stressed the role of the solar wind exposure timescale. Space weathering processes remain poorly investigated in the case of other types of asteroids, and they are still unclear in the case of outer Solar System bodies, due to a strong dependence of the weathering process on the original composition.  相似文献   

12.
In this paper we present quantitative results of observations of energetic neutral atoms (ENAs) originating from the lunar surface. These ENAs, which are hydrogen atoms, are the result of the solar wind protons being reflected from and neutralised at the surface of the Moon. These measurements were made with IBEX-Lo on NASA's IBEX satellite. From these measurements we derive the energy spectrum of the ENAs, their flux, and the lunar albedo for ENAs (i.e., the ratio of ENAs to the incoming solar wind protons). The energy spectra of the ENAs clearly show that their origin is directly from the solar wind via backscattering, and that they are not sputtered atoms. From several observation periods we derived an average global albedo of AH=0.09±0.05. From the observed energy spectra we derive a generic spectrum for unshielded bodies in the solar wind.  相似文献   

13.
We find the lunar darkening process could be due neither to simple addition of impact-melted glass nor to addition of devitrified glass to crushed lunar rock. There is evidence that lunar soil grains have thin, very light-absorbing coatings that mask absorption bands, seen in the reflection spectra of freshly crushed lunar rock, in the same manner as they are masked in the spectra of lunar soils. We believe the processes that produce these coatings are (1) deposition of atoms sputtered from lunar soil grains by solar wind particles and (2) deposition of vapor species vaporized from lunar soil grains by micrometeorite impacts. Coatings produced in laboratory simulations of these processes owe their strong light-absorbing properties in large part to the presence of abundant metallic Fe grains smaller than 100 Å in diameter. Another process, which depends on implantation of solar wind protons in lunar soil grains and their later mobilization during micrometeorite impacts to produce metallic Fe in the impact glass, also seems reasonable but has not yet been demonstrated experimentally. As a result of impact vaporization the Moon would preferentially lose minor amounts of light elements, principally monatomic oxygen, and this would result in oxygen depletion in the vapor condensate. This type of fraction would be more extreme on airless bodies with lower escape velocities. Sputtering occurs at higher effective temperatures and this would cause loss of all common rock-forming elements in approximately equal amounts. There would be some bias in this process toward retention of very heavy trace elements— a characteristic that has been observed in the lunar soil. This bias would be less important for smaller airless bodies. We describe an apparent new type of fractionation that occurs during deposition of sputtered atoms. This fractionation favors retention of higher mass atoms over lower mass atoms, and appears to be a linear function of mass. This may explain observed isotopic fractionations in lunar soil, in which the heavier isotope always appears to be enriched relative to the lighter one. This “first bounce fractionation” process should operate on all airless bodies. Na and K apparently do not conform to this fractionation process and have a much greater tendency to escape. This may help explain the presence of high Na concentrations around Io.  相似文献   

14.
Solar quiescent active regions are known to exhibit radio emission from discrete structures. The knowledge of their dimensions and brightness temperatures is essential for understanding the physics of quiescent, confined plasma regions. Solar eclipses of 10 August, 1980 and 26 January, 1990, observed with high sensitivity and high time resolution at 22 GHz, allowed an unprecedented opportunity to identify Fresnel diffraction effects during lunar occultations of active regions. The results indicate the presence of quiescent discrete sources smaller than one arcsecond in one dimension. Assuming symmetrical sources, their brightness temperatures were larger than 2 × 107 K and 8 × 107 K, for the 1980 and 1990 observations, respectively.In memoriam, 1942–1981.  相似文献   

15.
There is good evidence for the existence of very small amounts of methane, ammonia and carbon dioxide in the very tenuous lunar atmosphere which consists primarily of the rare gases helium, neon and argon. All of these gases, except40Ar, originate from solar wind particles which impinge on the lunar surface and are imbedded in the surface material. Here they may form molecules before being released into the atmosphere, or may be released directly, as is the case for rare gases. Evidence for the existence of the molecular gas species is based on the pre-dawn enhancement of the mass peaks attributable to these compounds in the data from the Apollo 17 Lunar Mass Spectrometer. Methane is the most abundant molecular gas but its concentration is exceedingly low, 1 × 103 mol cm?3, slightly less than36Ar, whereas the solar wind flux of carbon is approximately 2000 times that of36Ar. Several reasons are advanced for the very low concentration of methane in the lunar atmosphere.  相似文献   

16.
Abstract— Several solar gas rich lunar soils and breccias have trapped 40Ar/36Ar ratios >10, although solar Ar is expected to yield a ratio of <0.01. Radiogenic 40Ar produced in the lunar crust from 40K decay was outgassed into the lunar atmosphere, ionized, accelerated in the electromagnetic field of the solar wind, and reimplanted into lunar surface material. The 40Ar loss rate depends on the decreasing abundance of 40K. In order to calibrate the time dependence of the 40Ar/36Ar ratio in lunar surface material, the period of reimplantation of lunar atmospheric ions and of solar wind Ar was determined using the 235U‐136Xe dating method that relies on secondary cosmic‐ray neutron‐induced fission of 235U. We identified the trapped, fissiogenic, and cosmogenic noble gases in lunar breccia 14307 and lunar soils 70001‐8, 70181, 74261, and 75081. Uranium and Th concentrations were determined in the 74261 soil for which we obtain the 235U‐136Xe time of implantation of 3.25+0.38‐0.60 Ga ago. On the basis of several cosmogenic noble gas signatures we calculate the duration of this near surface exposure of 393 ± 45 Ma and an average shielding depth below the lunar surface of 73 ± 7 g/cm2. A second, recent exposure to solar and cosmic‐ray particles occurred after this soil was excavated from Shorty crater 17.2 ± 1.4 Ma ago. Using a compilation of all lunar data with reliable trapped Ar isotopic ratios and pre‐exposure times we infer a calibration curve of implantation times, based on the trapped40 Ar/36Ar ratio. A possible trend for the increase with time of the solar 3He/4He and 20Ne/22Ne ratios of about 12%/Ga and about 2%/Ga, respectively, is also discussed.  相似文献   

17.
Y. C. Whang 《Solar physics》1970,14(2):489-502
This paper presents a continued study of the two-dimensional guiding-center model of the solar wind interaction with the Moon. The characteristics theory and the computational method are discussed. The magnetic permeability of plasma is (1 + /2)–1 in the solar wind flow upstream of the Moon, and it changes to 1 in the void region of the lunar wake. The gradual change of the magnetic permeability in the penumbral region from the interplanetary condition to the void condition is explained as the source of field perturbations in the lunar wake. Perturbations of the magnetic field propagate as magnetoacoustic waves in a frame of reference moving with the plasma flow. Computer solutions were obtained to show that (i) the two principal perturbations of the magnetic field in the lunar wake (the umbral increase and the penumbral decrease) are confined to a region bounded by a Mach cone tangent to the lunar body, and (ii) the penumbral increases occur outside the lunar Mach cone. Computer solutions are also used to identify the source of field perturbations and to simulate the solar wind-moon interaction under varying interplanetary conditions.  相似文献   

18.
We present models of the spectral reflectances of groups of outer Solar System objects defined primarily by their colors in the spectral region 0.4–1.2 mu;m, and which have geometric albedo ～0.04 at wavelength 0.55 μm. Our models of the groups with the strongest reflectance gradients (reddest colors) use combinations of organic tholins. We test the hypothesis that metal-reddened igneous rock-forming minerals contribute to the red colors of Centaurs and KBOs by using the space-weathered lunar soil as one of the components of our models. We find that our models can admit the presence of moderate amounts of space-weathered (metal-reddened) minerals, but that they do not require this material to achieve the red colors of the reddest outer Solar System bodies. Our models with organic tholins are consistent with the results of other investigators.  相似文献   

19.
In contrast to earth, the atmosphere of the moon is exceedingly tenuous and appears to consist mainly of noble gases. The solar wind impinges on the lunar surface, supplying detectable amounts of helium, neon and 36Ar. Influxes of solar wind protons and carbon and nitrogen ions are significant, but atmospheric gases containing these elements have not been positively identified. Radiogenic 40Ar and 222Rn produced within the moon have been detected. The present rate of effusion of argon from the moon accounts for about 0.4% of the total production of 40Ar due to decay of 40K if the average abundance of potassium in the moon is 1000 ppm. Lack of weathering processes in the regolith suggests that most of the atmospheric 40Ar originates deep in the lunar interior, perhaps in a partially molten core. If so, other gases may be vented along with the argon.  相似文献   

20.
Abstract Helium and neon were extracted from individual lunar ilmenite grains, approximately 100 μm in diameter, using a pulsed step-heating technique. Grains from lunar samples 71501 and 79035, believed to have been exposed to solar corpuscular radiation at greatly different times, were studied. The results found were consistent with the hypothesis that in addition to solar-wind-implanted gas, a second more deeply implanted component was present in both species of grains. Average isotopic ratios were determined giving equal weight to each of the particles. As found in depth studies employing chemical etching, both the 3He/4He and 20He/22Ne ratios were lower in the more deeply implanted gas than in the solar wind component. The 3He/4He ratio in the solar wind component of the more ancient grains was lower than that in the more recently exposed ones, whereas no difference was found for the more deeply embedded He. In the deeply embedded component of the ancient grains, the 4He/20Ne ratio was ～2×that found in the more recently exposed grains. In the shallowly implanted component, the ratio varied greatly from grain to grain, preventing comparison with the solar wind elemental composition.  相似文献   

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