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1.
Abstract— On September 8, 2004, Genesis, a manmade space capsule, plummeted to Earth after almost three years in space. A ground‐based infrasound array was deployed to Wendover, Nevada, to measure the “hypersonic boom” from the reentry, since the expected initial reentry speed of the body was about 11 km/sec. Due to the complete failure of its dual parachute system, we had a unique opportunity to assess the degree of reliability of our previously developed relations for natural meteors and bolides to analyze this well‐characterized manmade body. At ?20–50 km from the nominal trajectory, we succeeded in recording over two minutes of infrasonic signals from Genesis. Here we report on subsequent analyses of these infrasonic data, including an assessment of the expected entry characteristics on the basis of a bolide/meteor/fireball entry model specifically adapted to modeling reentering manmade objects. From these simulations, we were able to evaluate the line source blast wave relaxation radius, the differential acoustic efficiency, etc., to compute an approximate total power balance during entry. Next, we analyzed the detailed signals arriving from Genesis using a numerical, signal detection and wave processing software package (Matseis/Infra_Tool). We established the initial and subsequent arrivals and evaluated its plane wave back azimuths and elevation arrival angles and the degree of maximum, pair‐wise cross‐correlation, its power spectrum, spectrogram analysis, standard seismic f‐k analysis, etc. From the associated entry parameters, we computed the kinetic energy density conservation properties for the propagating line source blast waves and compared these predictions against observed ground‐based infrasound amplitude and wave period data as a function of range. We discovered that previously computed differential acoustic efficiencies were unreliable at Mach numbers below about 10. This is because we had assumed that a line source explosion was applicable, whereas at very low Mach numbers, typical of recovered meteorites, the detailed source characteristics are closer to those of supersonic objects. When corrections for these unphysical, very high efficiencies were made, agreement between theory and observations improved. We also made an assessment for the energy of the blast wave source from the ground‐based infrasound data using several other techniques that were also adapted from previous bolide studies. Finally, we made a top‐down‐bottom‐up assessment of the line source wave normals propagating via refraction downward into the complex middle atmospheric environment. This assessment proved to be generally consistent with the digital signal processing analysis and with the observed time delay between the known Genesis reentry and the infrasonic observations.  相似文献   

2.
Abstract— The sound production from the Morávka fireball has been examined in detail making use of infrasound and seismic data. A detailed analysis of the production and propagation of sonic waves during the atmospheric entry of the Morávka meteoroid demonstrates that the acoustic energy was produced both by the hypersonic flight of the meteoroid (producing a cylindrical blast wave) and by individual fragmentation events of the meteoroid, which acted as small explosions (producing quasispherical shock waves). The deviation of the ray normals for the fragmentation events was found to be as much as 30° beyond that expected from a purely cylindrical line source blast. The main fragmentation of the bolide was confined to heights above 30 km with a possible maximum in acoustic energy production near 38 km. Seismic stations recorded both the direct arrival of the airwaves (the strongest signal) as well as air‐coupled P‐waves and Rayleigh waves (earlier signals). In addition, deep underground stations detected the seismic signature of the fireball. The seismic data alone permit reconstruction of the fireball trajectory to a precision on the order of a few degrees. The velocity of the meteoroid is much less well‐determined by these seismic data. The more distant infrasonic station detected 3 distinct signals from the fireball, identified as a thermospheric return, a stratospheric return, and an unusual mode propagating through the stratosphere horizontally and then leaking to the receiver.  相似文献   

3.
The orbital evolution of the two meteorites Příbram and Neuschwanstein on almost identical orbits and also several thousand clones were studied in the framework of the N-body problem for 5,000 years into the past. The meteorites moved on very similar orbits during the whole investigated interval. We have also searched for photographic meteors and asteroids moving on similar orbits. There were five meteors found in the IAU MDC database and six NEAs with currently similar orbits to Příbram and Neuschwanstein. However, only one meteor 161E1 and one asteroid 2002 QG46 had a similar orbital evolution over the last 2,000 years.  相似文献   

4.
Abstract— On January 15, 2006, Stardust, a man‐made space capsule, plummeted to Earth for a soft landing after spending seven years in space. Since the expected initial speed of the body was about 12.9 km/s, a four‐element ground‐based infrasound array was deployed to Wendover, Nevada, USA, to measure the hypersonic booms from the re‐entry. At a distance of ～33 km from the nominal trajectory, we easily recorded the weak acoustic arrivals and their continued rumbling after the main hypersonic boom arrival. In this paper, we report on subsequent analyses of these data, including an assessment of the expected entry characteristics (dynamics, energetics, ablation and panchromatic luminosity, etc.) on the basis of a bolide/meteor/fireball entry model that was specifically adapted for modeling a re‐entering man‐made object. Throughout the infrasonic data analyses, we compared our results for Stardust to those previously obtained for Genesis. From the associated entry parameters, we were also able to compute the kinetic energy density conservation properties for the propagating line source blast wave and compared the inviscid theoretical predictions against observed ground‐based infrasound amplitude and wave period data as a function of range. Finally, we made a top‐down bottom‐up assessment of the line source wave normals propagating downward into the complex temperature/sound speed and horizontal wind speed environment during January 15, 2006. This assessment proved to be generally consistent with the signal processing analysis and with the observed time delay between the known Stardust entry and the time of observations of infrasound signals, and so forth.  相似文献   

5.
On the basis of a ray tracing method the propagation and the attenuation of an auroral infrasonic wave are studied. Relations between the direct and reflected waves recorded at the Syowa Station, Antarctica, are clarified with regard to; (1) the delay time, (2) the intensity ratio, and (3) trace velocities. The time required for a wave to travel from the source to the ground is calculated as a function of a source altitude. The retardation time of the wave arrival behind the zenith crossing of the source current is deduced. A method is proposed for estimating the altitude of a source current from the retardation and a trace velocity of the wave. It is concluded that the existence of a supersonic equatorward motion of an electrojet which continues for a certain distance is necessary for the observation of auroral infrasonic waves. This distance must exceed at least 60 km equatorwards from the zenith to enable the direct wave to be observed and with total length of 930 km to enable the reflected wave to be observed. From these conditions it is also concluded that the infrasonic wave is not seen in mid latitudes and the reflected wave is a rare phenomenon.  相似文献   

6.
System spectral analysis of temporal variations in the level of acoustic signals recorded at a number of European infrasound stations is carried out. The prevailing periods that varied within 3–5 s are found. Initial kinetic and acoustic energies of the Romanian meteoroid and infrasound parameters are calculated: celerity (280 m/s), acoustic efficiency, and stratospheric wind velocity (about 20 m/s). Parameters of cylindrical and explosive shock waves are found: duration, characteristic size, and amplitude. The dependence of the attenuation of infrasonic waves on distance is estimated. The results of the estimates are in good agreement with the results of the observations.  相似文献   

7.
Abstract— Terminal bursts and fragmentations of meteoritic fireballs in the atmosphere may now be accurately located in four dimensions (three spatial + temporal) using seismic arrival times of their acoustic waves recorded by seismometer, camera, microphone, and/or infrasound stations on the ground. A computer program, SUPRACENTER, calculates travel times by ray tracing through realistic atmospheres (that include winds) and locates source positions by minimization of travel time residuals. This is analogous to earthquake hypocenter location in the solid Earth but is done through a variably moving medium. Inclusion of realistic atmospheric ray tracing has removed the need for the simplifying assumption of an isotropic atmosphere or an approximation to account for “wind drift.” This “drift” is on the order of several km when strong, unidirectional winds are present in the atmosphere at the time of a fireball's occurrence. SUPRACENTER‐derived locations of three seismically recorded fireballs: 1) the October 9, 1997 El Paso superbolide; 2) the January 25, 1989 Mt. Adams fireball; and 3) the May 6, 2000 Morávka fireball (with its associated meteorite fall), are consistent with (and, probably, an improvement upon) the locations derived from eyewitness, photographic, and video observations from the respective individual events. If direct acoustic seismic arrivals can be quickly identified for a fireball event, terminal burst locations (and, potentially, trajectory geometry and velocity information) can be quickly derived, aiding any meteorite recovery efforts during the early days after the fall. Potentially, seismic records may yield enough trajectory information to assist in the derivation of orbits for entering projectiles.  相似文献   

8.
Abstract— The fireball accompanying the Park Forest meteorite fall (L5) was recorded by ground‐based videographers, satellite systems, infrasound, seismic, and acoustic instruments. This meteorite shower produced at least 18 kg of recovered fragments on the ground (Simon et al. 2004). By combining the satellite trajectory solution with precise ground‐based video recording from a single site, we have measured the original entry velocity for the meteoroid to be 19.5 ± 0.3 km/s. The earliest video recording of the fireball was made near the altitude of 82 km. The slope of the trajectory was 29° from the vertical, with a radiant azimuth (astronomical) of 21° and a terminal height measured by infrared satellite systems of 18 km. The meteoroid's orbit has a relatively large semi‐major axis of 2.53 ± 0.19 AU, large aphelion of 4.26 ± 0.38 AU, and low inclination. The fireball reached a peak absolute visual magnitude of ?22, with three major framentation episodes at the altitudes of 37, 29, and 22 km. Acoustic recordings of the fireball airwave suggest that fragmentation was a dominant process in production of sound and that some major fragments from the fireball remained supersonic to heights as low as ?10 km. Seismic and acoustic recordings show evidence of fragmentation at 42, 36, 29, and 17 km. Examination of implied energies/initial masses from all techniques (satellite optical, infrasound, seismic, modeling) leads us to conclude that the most probable initial mass was (11 ± 3) × 103 kg, corresponding to an original energy of ?0.5 kt TNT (2.1 times 1012 J) and a diameter of 1.8 m. These values correspond to an integral bolometric efficiency of 7 ± 2%. Early fragmentation ram pressures of <1 MPa and major fragmentations occurring with ram pressures of 2–5 MPa suggest that meter‐class stony near‐Earth asteroids (NEAs) have tensile strengths more than an order of magnitude lower than have been measured for ordinary chondrites. One implication of this observation is that the rotation period for small, fast‐rotating NEAs is likely to be >30 seconds.  相似文献   

9.
Abstract— We report Rb-Sr analyses of phosphates from nine ordinary chondrites, more than doubling the number of meteorites for which such data are available. Ordinary chondrite phosphates characteristically have Rb/Sr ratios sufficiently low to permit accurate identification of initial 87Sr/86Sr, which is generally (but not in all cases) found to be significantly higher than the more primitive initial 87Sr/86Sr ratios inferred for carbonaceous chondrite refractory inclusions (ALL), basaltic achondrites (BABI), or bulk ordinary chondrites (in the ALL-BABI range). Such elevation of initial 87Sr/86Sr is generally considered to reflect isotopic redistribution during metamorphism, and with a model for Rb/Sr in this environment can lead to an inferred metamorphic timescale. For whole rock Rb/Sr the inferred formation intervals are typically tens of Ma (range nil to > 100 Ma). There is no evident relation between initial Sr elevation and metamorphic grade. There is not a clear difference in initial Sr effects between H and L chondrites; LL chondrites show much less (if any) elevation of initial Sr, but data are available for only two meteorites. For the first time it is possible to make a detailed comparison of initial Sr and I-Xe chronologies for several meteorites: these two potential metamorphic chronometers conspicuously fail to agree, in terms of both age and sequence of ages. A comparably definitive assessment of the comparison between initial Sr and Pb-Pb chronologies is not yet possible, but presently available data suggest that these two approaches to chondrite chronology also fail to agree. Without a correlation with metamorphic grade, or detailed agreement with an independent chronometer, it remains unclear whether initial 87Sr/86Sr in phosphates can be translated into a reliable chronometer for ordinary chondrite metamorphism, at least within simple interpretational frameworks.  相似文献   

10.
Abstract— An impressive daylight fireball was observed from Spain, Portugal, and the south of France at 16h46m45s UTC on January 4, 2004. The meteoroid penetrated into the atmosphere, generating shock waves that reached the ground and produced audible booms. The associated airwave was recorded at a seismic station located 90 km north of the fireball trajectory in Spain, and at an infrasound station in France located 750 km north‐east of the fireball. The absolute magnitude of the bolide has been determined to be ?18 ± 1 from a casual video record. The energy released in the atmosphere determined from photometric, seismic, and infrasound data was about 0.02 kilotons (kt). A massive fragmentation occurred at a height of 28 ± 0.2 km, resulting in a meteorite strewn field of 20 × 6 km. The first meteorite specimen was found on January 11, 2004, near the village of Villalbeto de la Peña, in northern Palencia (Spain). To date, about 4.6 kg of meteorite mass have been recovered during several recovery campaigns. The meteorite is a moderately shocked (S4) L6 ordinary chondrite with a cosmic‐ray‐exposure age of 48 ± 5 Ma. Radioisotope analysis shows that the original body had a mass of 760 ± 150 kg, which is in agreement with the estimated mass obtained from photometric and seismic measurements.  相似文献   

11.
Abstract— The properties and history of the parent meteoroid of the Morávka H5–6 ordinary chondrites have been studied by a combination of various methods. The pre‐atmospheric mass of the meteoroid was computed from fireball radiation, infrasound, seismic signal, and the content of noble gases in the meteorites. All methods gave consistent results. The best estimate of the pre‐atmospheric mass is 1500 ± 500 kg. The fireball integral bolometric luminous efficiency was 9%, and the acoustic efficiency was 0.14%. The meteoroid cosmic ray exposure age was determined to be (6.7 ± 1.0) × 106 yr. The meteorite shows a clear deficit of helium, both 3He and 4He. This deficit can be explained by solar heating. Numerical backward integration of the meteoroid orbit (determined in a previous paper from video records of the fireball) shows that the perihelion distance was probably lower than 0.5 AU and possibly as low as 0.1 AU 5 Ma ago. The collision which excavated Morávka probably occurred while the parent body was on a near‐Earth orbit, as opposed to being confined entirely to the main asteroid belt. An overview of meteorite macroscopic properties, petrology, mineralogy, and chemical composition is given. The meteorites show all mineralogical features of H chondrites. The shock level is S2. Minor deviations from other H chondrites in abundances of trace elements La, Ce, Cs, and Rb were found. The ablation crust is enriched with siderophile elements.  相似文献   

12.
Abstract— During preliminary examination of 81P/Wild 2 particles collected by the NASA Stardust spacecraft, we analyzed seven, sulfur embedded and ultramicrotomed particles extracted from five different tracks. Sections were analyzed using a scanning transmission X‐ray microscope (SXTM) and carbon X‐ray absorption near edge structure (XANES) spectra were collected. We compared the carbon XANES spectra of these Wild 2 samples with a database of spectra on thirty‐four interplanetary dust particles (IDPs) and with several meteorites. Two of the particles analyzed are iron sulfides and there is evidence that an aliphatic compound associated with these particles can survive high temperatures. An iron sulfide from an IDP demonstrates the same phenomenon. Another, mostly carbon free containing particle radiation damaged, something we have not observed in any IDPs we have analyzed or any indigenous organic matter from the carbonaceous meteorites, Tagish Lake, Orgueil, Bells and Murchison. The carbonaceous material associated with this particle showed no mass loss during the initial analysis but chemically changed over a period of two months. The carbon XANES spectra of the other four particles varied more than spectra from IDPs and indigenous organic matter from meteorites. Comparison of the carbon XANES spectra from these particles with 1. the carbon XANES spectra from thirty‐four IDPs (<15 micron in size) and 2. the carbon XANES spectra from carbonaceous material from the Tagish Lake, Orgueil, Bells, and Murchison meteorites show that 81P/Wild 2 carbon XANES spectra are more similar to IDP carbon XANES spectra then to the carbon XANES spectra of meteorites.  相似文献   

13.
Abstract— During the early morning hours of the night of the peak of the annual Leonid meteor shower on 1998 November 17, a bright fireball (approximately ?12 to ?14 visual magnitude at 100 km in the zenith) was observed over northern New Mexico with visual sightings as far away from Los Alamos as Albuquerque (～150 km to the south of Los Alamos), including direct persistent trail observations at the U. S. A. F. Starfire Optical Range (SOR), which is also near Albuqerque. This event did not produce any sonic boom reports, presumably because of its high altitude. It was also detected locally by an infrared radiometer at Sandia National Laboratory and by an intensified charge-coupled device (CCD) camera located in Placitas, New Mexico. Subsequent investigations of the data from the six infrasound arrays used by Los Alamos National Laboratory (LANL) and operated for the Department of Energy as a part of the Comprehensive Test Ban Treaty (CTBT) Research and Development program for the International Monitoring System (IMS) showed the presence of an infrasonic signal from the proper direction at the correct time for this bolide from two of our six arrays (both located in Los Alamos). The infrasound recordings (i.e., the wave amplitude and period data) indicated that an explosion occurred in the atmosphere at a source height of ～93.5 km (with respect to sea level) or ～90 km with respect to the altitude of Los Alamos, having its origins slightly to the north and west of Los Alamos. Purely geometric solutions from the ground observers reports combined with direct measurements from the CCD camera at Placitas produced a source height of 91 ± 7 km. The signal characteristics analyzed from 0.5 to 3.0 Hz include a total duration of about 3–4 s for a source directed from Los Alamos toward 353.6 ± 0.4° measured from true north at a maximum elevation arrival angle of ～72.7°. The latter was deduced on the basis of the observed signal trace velocities (for the part of the recording with the highest cross-correlation) and ranged from a constant value of about 920–1150 m/s (depending on the window length used in the analysis) for a ray trajectory along a direct refractive path between the source and the Los Alamos arrays. The dominant signal frequency at maximum amplitude at Los Alamos was ～0.71 Hz. These highly correlated signals had a peak to peak, maximum amplitude of ～2.1 microbars (0.21 Pa). Using several methods that incorporate various observed signal characteristics, total distance traveled, etc., our analysis indicates that the bolide probably had a source energy of ～1.14 t (TNT equivalent) or 4.77 × 109 J. This is ～14.1× smaller than the source energy estimate made using the infrasonic, empirical source energy relationship for low-altitude stationary point sources developed in the 1960s by the Air Force Technical Applications Center (AFTAC), Patrick Air Force Base, Florida. This relation was originally developed, however, for much larger source energies and at much longer ranges.  相似文献   

14.
Abstract– The Grimsby meteorite (H4–6) fell on September 25, 2009. As of mid‐2010, 13 fragments totaling 215 g have been recovered. Records of the accompanying fireball from the Southern Ontario Meteor Network, including six all‐sky video cameras, a large format CCD, infrasound and radar records, have been used to characterize the trajectory, speed, orbit, and initial mass of the meteoroid. From the four highest quality all‐sky video records, the initial entry velocity was 20.91 ± 0.19 km s?1 while the derived radiant has a local azimuth of 309.40° ± 0.19° and entry angle of 55.20° ± 0.13°. Three major fragmentation episodes are identified at 39, 33, and 30 km height, with corresponding uncertainties of approximately 2 km. Evidence for early fragmentation at heights of approximately 70 km is found in radar data; dynamic pressure of this earliest fragmentation is near 0.1 MPa while the main flare at 39 km occurred under ram pressures of 1.5 MPa. The fireball was luminous to at least 19.7 km altitude and the dynamic mass estimate of the largest remaining fragment at this height is approximately several kilograms. The initial mass is constrained to be <100 kg from infrasound data and ablation modeling, with a most probable mass of 20–50 kg. The preatmospheric orbit is typical of an Apollo asteroid with a likely immediate origin in either the 3:1 or ν6 resonances.  相似文献   

15.
We report the results of nominally anhydrous equilibrium and fractional crystallization experiments on a synthetic Yamato‐980459 (Y98) bulk composition at 0.5 GPa. These experiments allow us to test a suggested fractional crystallization model, calculated using MELTS by Symes et al. ( 2008 ), in which a Y98‐like initial liquid yielded a magma closely resembling the bulk composition of QUE 94201. Although the two meteorites cannot be cogenetic owing to their age difference, they are thought to represent bona fide magmatic liquids rather than products of crystal accumulation, as are most Martian basaltic meteorites. Hence, understanding possible petrogenetic links between these types of liquids could be revealing about processes of melting and crystallization that formed the range of Martian basalts. We find that Y98 can, in fact, generate a residual liquid closely resembling QUE, but only after a very different crystallization process, and different degree of crystallization, than that modeled using MELTS. In addition, both the identity and sequence of crystallizing phases are very different between model and experiments. Our fractional crystallization experiments do not produce a QUE‐like liquid, and the crystallizing phases are an even poorer match to the MELTS‐calculated compositions than in the equilibrium runs. However, residual liquids from our experiments define a liquid line of descent that encompasses bulk compositions of parental melts calculated for several Martian basaltic meteorites, suggesting that the known Martian basaltic meteorites had their ultimate origin from the same or very similar source lithologies. These are, in turn, similar to source rocks modeled by previous studies as products of extensive crystallization of an initial Martian magma ocean.  相似文献   

16.
We present the infrasonic observations of three large bolides that were observed at numerous International Monitoring System (IMS) infrasound arrays on a global scale. First, a simple procedure for the global association of infrasound detections from large infrasound events is outlined. Infrasound signals are associated with large events based on arrival time, backazimuth and uniqueness at a given IMS array. Next, we apply the algorithm to three bolides and investigate some of the factors affecting the detectability of infrasound from large events. Our findings suggest that site-noise effects significantly degrade the capability of the IMS infrasound network, suggesting that more effort is required to reduce ambient site noise. These results have implications for the use of infrasound measurements (in particular those from IMS stations) as a tool for evaluating the global flux of near-Earth objects.  相似文献   

17.
Lunar meteorites provide important new samples of the Moon remote from regions visited by the Apollo and Luna sample return missions. Petrologic and geochemical analysis of these meteorites, combined with orbital remote sensing measurements, have enabled additional discoveries about the composition and age of the lunar surface on a global scale. However, the interpretation of these samples is limited by the fact that we do not know the source region of any individual lunar meteorite. Here, we investigate the link between meteorite and source region on the Moon using the Lunar Prospector gamma ray spectrometer remote sensing data set for the elements Fe, Ti, and Th. The approach has been validated using Apollo and Luna bulk regolith samples, and we have applied it to 48 meteorites excluding paired stones. Our approach is able broadly to differentiate the best compositional matches as potential regions of origin for the various classes of lunar meteorites. Basaltic and intermediate Fe regolith breccia meteorites are found to have the best constrained potential launch sites, with some impact breccias and pristine mare basalts also having reasonably well‐defined potential source regions. Launch areas for highland feldspathic meteorites are much less well constrained and the addition of another element, such as Mg, will probably be required to identify potential source regions for these.  相似文献   

18.
Identification and characterization of small extraterrestrial samples, such as small Antarctic meteorites <~1 cm, require the development of convenient laboratory‐based nondestructive analytical techniques using X‐ray diffraction (XRD). We explore the characterization criteria using an X‐ray diffractometer with a Gandolfi attachment using sub‐mm small fragments and powder aggregates for various kinds of stony meteorites and develop a new analytical technique. We primarily focus on olivine and pyroxene because they are the most abundant and important minerals for stony meteorite classification. A new calibration is performed to estimate the FeO content of the olivine in unequilibrated ordinary chondrites, which is useful for determining the meteorite chemical group irrespective of powder aggregate diameter but dependent on fragment grain diameter. This is because X‐ray intensity absorption is more effective for grains than for powders. Clinoenstatite (Cen) and orthoenstatite (Oen) were distinguished using the presence or absence of the isolated Oen 511 index peak. The method is also applied to other stony meteorites including carbonaceous chondrites and achondrites. The XRD results are consistent with studies based on polished sections involving textural observations by scanning microscope and chemical compositions of the constituent minerals. The new measurement technique presented here is convenient because of its use in air by the laboratory‐based X‐ray diffractometer, which makes it useful for the initial analyses of restricted extraterrestrial sample characterization.  相似文献   

19.
Data from infrasound stations are used to determine the basic parameters of infrasonic waves generated during the passage and airburst of the Chelyabinsk space body: time lag, duration, spectral structure, dispersion dependence, and celerity. A simulation is performed for the parameters of the infrasonic waves. A comparison between the simulation and observation results shows a good agreement.  相似文献   

20.
Abstract— The major element, trace element, and isotopic compositional ranges of the martian basaltic meteorite source regions have been modeled assuming that planetary differentiation resulted from crystallization of a magma ocean. The models are based on low to high pressure phase relationships estimated from experimental runs and estimates of the composition of silicate Mars from the literature. These models attempt to constrain the mechanisms by which the martian meteorites obtained their superchondritic CaO/Al2O3 ratios and their source regions obtained their parent/daughter (87Rb/86Sr, 147Sm/144Nd, and 176Lu/177Hf) ratios calculated from the initial Sr, Nd, and Hf isotopic compositions of the meteorites. High pressure experiments suggest that majoritic garnet is the liquidus phase for Mars relevant compositions at or above 12 GPa. Early crystallization of this phase from a martian magma ocean yields a liquid characterized by an elevated CaO/Al2O3 ratio and a high Mg#. Olivine‐pyroxene‐garnet‐dominated cumulates that crystallize subsequently will also be characterized by superchondritic CaO/Al2O3 ratios. Melting of these cumulates yields liquids with major element compositions that are similar to calculated parental melts of the martian meteorites. Furthermore, crystallization models demonstrate that some of these cumulates have parent/daughter ratios that are similar to those calculated for the most incompatible‐element‐depleted source region (i.e., that of the meteorite Queen Alexandra [QUE] 94201). The incompatible‐element abundances of the most depleted (QUE 94201‐like) source region have also been calculated and provide an estimate of the composition of depleted martian mantle. The incompatible‐element pattern of depleted martian mantle calculated here is very similar to the pattern estimated for depleted Earth's mantle. Melting the depleted martian mantle composition reproduces the abundances of many incompatible elements in the parental melt of QUE 94201 (e.g., Ba, Th, K, P, Hf, Zr, and heavy rare earth elements) fairly well but does not reproduce the abundances of Rb, U, Ta and light rare earth elements. The source regions for meteorites such as Shergotty are successfully modeled as mixtures of depleted martian mantle and a late stage liquid trapped in the magma ocean cumulate pile. Melting of this hybrid source yields liquids with major element abundances and incompatible‐element patterns that are very similar to the Shergotty bulk rock.  相似文献   

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