ABOUT THIS COLLECTION

Meteoritics & Planetary Science is an international monthly journal of the Meteoritical Society—a scholarly organization promoting research and education in planetary science. Topics include the origin and history of the solar system, planets and natural satellites, interplanetary dust and interstellar medium, lunar samples, meteors and meteorites, asteroids, comets, craters, and tektites.

Meteoritics & Planetary Science was first published in 1935 under the title Contributions of the Society for Research on Meteorites. In 1947, the publication became known as Contributions of the Meteoritical Society and continued through 1951. From 1953 to 1995, the publication was known as Meteoritics, and in 1996, the journal's name was changed to Meteoritics & Planetary Science or MAPS. The journal was not published in 1952 and from 1957 to 1964.

This archive provides access to Meteoritics & Planetary Science Volumes 37-44 (2002-2009).

Visit Wiley Online Library for new and retrospective Meteoritics & Planetary Science content (1935-present).

ISSN: 1086-9379

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Recent Submissions

  • Application of a textural geospeedometer to the late-stage magmatic history of MIL 03346

    Hammer, J. E. (The Meteoritical Society, 2009-01-01)
    Dynamic crystallization experiments performed on Fe-rich, Al-poor basalt are employed as a textural calibration set to quantify the late-stage igneous history of nakhlite Miller Range (MIL) 03346. The ratio of crystal-melt surface area to volume typifying morphologically distinct populations of Ca-pyroxene has been shown to vary as a strong function of cooling rate (Hammer 2006). Furthermore, a texture of phenocrysts surrounded by finer-grained groundmass crystals arises by sequential nucleation events during constant-rate cooling, but multiple populations nucleate only if the cooling rate is less than or equal to 72 degrees C h^(-1). Textural analysis of meteorite MIL 03346 reveals at least two distinct populations. The Ca-pyroxene phenocryst and microphenocryst three dimensional (3D) aspect ratios are 112 +/- 8.3 and 1530 +/- 160 mm^(-1), respectively. By comparison with the calibration set, the range of cooling rates consistent with 3D aspect ratios of both populations in MIL 03346 is ~20 degrees C h^(-1). An additional experiment was performed approximating a conductive heat transfer profile in order to interpret and apply results of constant-rate cooling experiments to the natural cooling of magma. Results suggest that the textures of constant-rate experiments parallel the initial period of rapid cooling in natural magma. Initial cooling rates of ~20 degrees C h^(-1) in the lava hosting MIL 03346 occur in conductively solidifying lava at depths of ~0.4 m, constraining the minimum total thickness to greater than or equal to 0.8 m. Crystal accumulation beginning in a subsurface reservoir and continuing after lava emplacement as an inflated pahoehoe sheet satisfies all textural constraints on the late-stage igneous history of MIL 03346.
  • The origin of the Brunflo fossil meteorite and extraterrestrial chromite in mid-Ordovician limestone from the Gärde quarry (Jämtland, central Sweden)

    Alwmark, C.; Schmitz, B. (The Meteoritical Society, 2009-01-01)
    The Brunflo fossil meteorite was found in the 1950s in mid-Ordovician marine limestone in the Grde quarry in Jmtland. It originates from strata that are about 5 million years younger than similar limestone that more recently has yielded >50 fossil meteorites in the Thorsberg quarry at Kinnekulle, 600 km to the south. Based primarily on the low TiO2 content (about 1.8 wt%) of its relict chromite the Brunflo meteorite had been tentatively classified as an H chondrite. The meteorite hence appears to be an anomaly in relation to the Kinnekulle meteorites, in which chromite composition, chondrule mean diameter and oxygen isotopic composition all indicate an L-chondritic origin, reflecting an enhanced flux of meteorites to Earth following the disruption of the L chondrite parent body 470 Ma. New chondrule-size measurements for the Brunflo meteorite indicate that it too is an L chondrite, related to the same parent-body breakup. Chromite maximum diameters and well-defined chondrule structures further show that Brunflo belongs to the L4 or L5 type. Chromites in recently fallen L4 chondrites commonly have low TiO2 contents similar to the Brunflo chromites, adding support for Brunflo being an L4 chondrite. The limestone in the Grde quarry is relatively rich (about 0.45 grain kg^(-1)) in sediment-dispersed extraterrestrial chromite grains (63 m) with chemical composition similar to those in L chondrites and the limestone (1-3 grains kg^(-1)) at Kinnekulle, suggesting that the enhanced flux of L chondrites prevailed, although somewhat diminished, at the time when the Brunflo meteorite fell.
  • Magnetic zones of Mars: Deformation-controlled origin of magnetic anomalies

    Kletetschka, G.; Lillis, R.; Ness, N. F.; Acuña, M. H.; Connerney, J. E. P.; Wasilewski, P. J. (The Meteoritical Society, 2009-01-01)
    Intense magnetic anomalies over Martian surface suggest preservation of large volumes of very old crust (>3 Gyr) that formed in the presence of a global magnetic field. The global distribution of the magnetic intensities observed above the Martian crust suggests a division into three zones. Zone 1 is where the magnetic signature is negligible or of relatively low intensity at Mars Global Surveyor (MGS) satellite mapping altitude (400 km). Zone 2 is the region of intermediate crustal magnetic amplitudes and zone 3 is where the highest magnetic intensities are measured. Crater demagnetization near zone 3 reveals the presence of rocks with both high magnetic intensity and coercivity. Magnetic analyses of terrestrial rocks show that compositional banding in orogenic zones significantly enhances both magnetic coercivity and thermal remanent magnetization (TRM) efficiency. Such enhancement offers a novel explanation for the anomalously large intensities inferred of magnetic sources on Mars. We propose that both large magnetic coercivity and intensity near the South Pole is indicative of the presence of a large degree of deformation. Associated compositional zoning creates conditions for large scale magnetic anisotropy allowing magnetic minerals to acquire magnetization more efficiently, thereby causing the distinct magnetic signatures in zone 3, expressed by intense magnetic anomalies. We use a simple model to verify the magnetic enhancement. We hypothesize that magnetically enhanced zone would reside over the down welling plume at the time of magnetization acquisition.
  • Physical distribution trends in Darwin glass

    Howard, Kieren T. (The Meteoritical Society, 2009-01-01)
    Darwin glass formed by impact melting, probably during excavation of the 1.2 km diameter Darwin crater, Tasmania, Australia. The glass was ejected up to 20 km from the source crater and forms a strewn field of 400 km^2. There is at least 11,250 m^3 of glass in the strewn field and relative to the size of the crater this is the most abundant ejected impact glass on Earth. The glass population can be subdivided on the basis of shape (74% irregular, 20% ropy, 0.5% spheroid, 6% droplet, and 0.7% elongate) and color (53% dark green, 31% light green, 11% black, and 5% white). The white glasses contain up to 92 wt% SiO2 and are formed from melting of quartzite. Black glasses contain a minimum of 76 wt% SiO2 and formed from melting of shale. Systematic variations in the proportion of glasses falling into each of the color and shape classes relative to distance from the crater show: 1) a decrease in glass abundance away from the crater; 2) the largest fragments of glass are found closest to the crater; 3) small fragments (2 g) dominate finds close to the crater; 4) the proportion of white glass is greatest closest to the crater; 5) the proportion of black glass increases with distance from the crater and 6) the proportion of splashform glasses increases with distance from the crater. These distribution trends can only be explained by the molten glass having been ballistically ejected from Darwin crater during impact and are related to 1) the depth of excavation from the target rock stratigraphy and/or 2) viscosity contrasts between the high and low SiO2 melt. The high abundance and wide distribution of ejected melt is attributed to a volatile charged target stratigraphy produced by surface swamps that are indicated by the paleoclimate record.
  • Lunar meteorite LaPaz Icefield 04841: Petrology, texture, and impact-shock effects of a low-Ti mare basalt

    Hill, E.; Taylor, L. A.; Floss, C.; Liu, Y. (The Meteoritical Society, 2009-01-01)
    Found during the 2004 U.S. Antarctic Search for Meteorites season, LaPaz Icefield (LAP) 04841 represents an addition to the LaPaz lunar basalts suite and brings the total mass collected to 1.93 kg. The presence of FeNi grains, troilite, and the anorthositic composition of plagioclase are evidence for the lunar origin of this meteorite. Pyroxene and olivine Mn/Fe values plot along the trend set for lunar basalts. Analyses of chromite grains provide a V/(Al + Cr) ratio of 1.33 +/- 13, translating to an fO2 one log unit below the IW buffer, in accordance with previous fO2 estimates for lunar basalts. Application of the Zr-cooling speedometer, for ilmenite and ulvspinel pairs, gives a cooling rate of 5.2 degrees C/day, matching previous estimates of cooling rates for the LaPaz lunar meteorites and Apollo mare basalts. Mineral modes and chemistries, as well as trace-element patterns, provide compelling evidence for pairing of this meteorite to others in the LaPaz lunar basalt suite.
  • Galactic cosmic ray-produced 129Xe and 131Xe excesses in troilites of the Cape York iron meteorite

    Mathew, K. J.; Marti, K. (The Meteoritical Society, 2009-01-01)
    The flux of galactic cosmic rays (GCR) in the solar system appears to change with time. Based on the abundances in iron meteorites of cosmogenic nuclides of different half lives, Lavielle et al. (1999) found that the GCR flux increased in recent times (<100 Ma) by about 38% compared to average flux in the past 150 Ma to 700 Ma ago. A promising technique for calibrating the GCR flux during the past ~50 Ma, based on the 129I and 129Xe pair of nuclides, was discussed earlier (Marti 1986; Murty and Marti 1987). The 129I-129Xen chronometer provides a shielding-independent system as long as the exposure geometry remained fixed. It is especially suitable for large iron meteorites (Te-rich troilite) because of the effects by the GCR secondary neutron component. Although GCR-produced Xe components were identified in troilites, several issues require clarifications and improvements; some are reported here. We developed a procedure for achieving small Xe extraction blanks which are required to measure indigenous Xe in troilites. The 129Xe and 131Xe excesses (129Xen, 131Xen) due to neutron reactions in Te are correlated in a stepwise release run during the troilite decomposition. Our data show that indigenous Xe in troilite of Cape York has isotopic abundances consistent with ordinary chondritic Xe (OC-Xe), in contrast to a terrestrial signature which was reported earlier. Two methods are discussed which assess and correct for an interfering radiogenic 129Xer component from extinct 129I. The corrected 129Xen concentration in troilite D4 of Cape York yields a cosmic ray exposure (CRE) age of 82 +/- 7 Ma consistent, within uncertainties, with reported data (Murty and Marti 1987; Marti et al. 2004).
  • Organic compound alteration during hypervelocity collection of carbonaceous materials in aerogel

    Spencer, M. K.; Clemett, S. J.; Sandford, S. A.; McKay, D. S.; Zare, R. N. (The Meteoritical Society, 2009-01-01)
    The NASA Stardust mission brought to Earth micron-size particles from the coma of comet 81P/Wild 2 using aerogel, a porous silica material, as the capture medium. A major challenge in understanding the organic inventory of the returned comet dust is identifying, unambiguously, which organic molecules are indigenous to the cometary particles, which are produced from carbon contamination in the Stardust aerogel, and which are cometary organics that have been modified by heating during the particle capture process. Here it is shown that 1) alteration of cometary organic molecules along impact tracks in aerogel is highly dependent on the original particle morphology, and 2) organic molecules on test-shot terminal particles are mostly preserved. These conclusions are based on two-step laser mass spectrometry ((L^2)MS) examinations of test shots with organic-laden particles (both tracks in aerogel and the terminal particles themselves).
  • Layered ejecta craters and the early water/ice aquifer on Mars

    Oberbeck, V. R. (The Meteoritical Society, 2009-01-01)
    A model for emplacement of deposits of impact craters is presented that explains the size range of Martian layered ejecta craters between 5 km and 60 km in diameter in the low and middle latitudes. The impact model provides estimates of the water content of crater deposits relative to volatile content in the aquifer of Mars. These estimates together with the amount of water required to initiate fluid flow in terrestrial debris flows provide an estimate of 21% by volume (7.6 x 10^7 km^3) of water/ice that was stored between 0.27 and 2.5 km depth in the crust of Mars during Hesperian and Amazonian time. This would have been sufficient to supply the water for an ocean in the northern lowlands of Mars. The existence of fluidized craters smaller than 5 km diameter in some places on Mars suggests that volatiles were present locally at depths less than 0.27 km. Deposits of Martian craters may be ideal sites for searches for fossils of early organisms that may have existed in the water table if life originated on Mars.
  • The Canyon Diablo impact event: Projectile motion through the atmosphere

    Artemieva, N.; Pierazzo, E. (The Meteoritical Society, 2009-01-01)
    Meteor Crater is one of the first impact structures systematically studied on Earth. Its location in arid northern Arizona has been ideal for the preservation of the structure and the surviving meteoric material. The recovery of a large amount of meteoritic material in and around the crater has allowed a rough reconstruction of the impact event: an iron object 50 m in diameter impacted the Earths surface after breaking up in the atmosphere. The details of the disruption, however, are still debated. The final crater morphology (deep, bowl-shaped crater) rules out the formation of the crater by an open or dispersed swarm of fragments, in which the ratio of swarm radius to initial projectile radius Cd is larger than 3 (the final crater results from the sum of the craters formed by individual fragments). On the other hand, the lack of significant impact melt in the crater has been used to suggest that the impactor was slowed down to 12 km/s by the atmosphere, implying significant fragmentation and fragments separation up to 4 initial radii. This paper focuses on the problem of entry and motion through the atmosphere for a possible Canyon Diablo impactor as a first but necessary step for constraining the initial conditions of the impact event which created Meteor Crater. After evaluating typical models used to investigate meteoroid disruption, such as the pancake and separated fragment models, we have carried out a series of hydrodynamic simulations using the 3D code SOVA to model the impactor flight through the atmosphere, both as a continuum object and a disrupted swarm. Our results indicate that the most probable pre-atmospheric mass of the Meteor Crater projectile was in the range of 4x10^8 to 1.2x10^9 kg (equivalent to a sphere 4666 m in diameter). During the entry process the projectile lost probably 30% to 70% of its mass, mainly because of mechanical ablation and gross fragmentation. Even in the case of a tight swarm of particles (Cd <3), small fragments can separate from the crater-forming swarm and land on the plains (tens of km away from the crater) as individual meteorites. Starting from an impactor pre-atmospheric velocity of ~18 km/s, which represents an average value for Earth-crossing asteroids, we find that after disruption, the most probable impact velocity at the Earths surface for a tight swarm is around 15 km/s or higher. A highly dispersed swarm would result in a much stronger deceleration of the fragments but would produce a final crater much shallower than observed at Meteor Crater.
  • Cosmogenic nuclides in the solar gas-rich H3–6 chondrite breccia Frontier Mountain 90174

    Leya, I.; Welten, K. C.; Nishiizumi, K.; Caffee, M. W. (The Meteoritical Society, 2009-01-01)
    We re-evaluated the cosmic-ray exposure history of the H36 chondrite shower Frontier Mountain (FRO) 90174, which previously was reported to have a simple exposure history, an irradiation time of about 7 Ma, and a pre-atmospheric radius of 80-100 cm (Welten et al. 2001). Here we measured the concentrations and isotopic compositions of He, Ne, and Ar in 8 aliquots of 6 additional fragments of this shower, and 10Be and 26Al in the stone fractions of seven fragments. The radionuclide concentrations in the stone fractions, combined with those in the metal fractions, confirm that all samples are fragments of the FRO 90174 shower. Four of the fragments contain solarwind- implanted noble gases with a solar 20Ne/22Ne ratio of ~12.0, indicating that FRO 90174 is a regolith breccia. The concentrations of solar gases and cosmogenic 21Ne in the samples analyzed by us and by Welten et al. (2001) overlap with those of the FRO H-chondrites from the 1984 season, suggesting that many of these samples are also part of the large FRO 90174 chondrite shower. The cosmogenic 21Ne concentrations in FRO 90174 show no simple correlation with 10Be and 26Al activities. We found 21Ne excesses between 0.3-1.1 x 10^(-8) cm3 STP/g in 6 of the 17 samples. Since excess 21Ne and trapped solar gases are not homogeneously distributed, i.e., we found in one fragment aliquots with and without excess 21Ne and solar 20Ne, we conclude that excess 21Ne is due to GCR irradiation of the regolith before compaction of the FRO 90174 object. Therefore, the chondrite shower FRO 90174 did not simply experience an exposure history, but some material was already irradiated at the surface of an asteroid leading to excess 21Ne. This excess 21Ne is correlated to implanted solar gases, clearly indicating that both processes occurred on the regolith.
  • Understanding the textures and origin of shock melt pockets in Martian meteorites from petrographic studies, comparisons with terrestrial mantle xenoliths, and experimental studies

    Walton, E. L.; Shaw, C. S. J. (The Meteoritical Society, 2009-01-01)
    We present a textural comparison of localized shock melt pockets in Martian meteorites and glass pockets in terrestrial, mantle-derived peridotites. Specific textures such as the development of sieve texture on spinel and pyroxene, and melt migration and reaction with the host rock are identical between these two apparently disparate sample sets. Based on petrographic and compositional observations it is concluded that void collapse/variable shock impedance is able to account for the occurrence of pre-terrestrial sulfate-bearing secondary minerals in the melts, high gas emplacement efficiencies, and S, Al, Ca, and Na enrichments and Fe and Mg depletion of shock melt compositions compared to the host rock; previously used as arguments against such a formation mechanism. Recent experimental studies of xenoliths are also reviewed to show how these data further our understanding of texture development and can be used to shed light on the petrogenesis of shock melts in Martian meteorites.
  • K-Ar dating of rocks on Mars: Requirements from Martian meteorite analyses and isochron modeling

    Bogard, D. D. (The Meteoritical Society, 2009-01-01)
    Radiometric age dating of Martian rocks and surfaces at known locations for which crater densities can be determined is highly desirable in order to fully understand Martian history. Performing K-Ar age dating of igneous rocks on Mars by robots, however, presents technical challenges. Some of these challenges can be defined by examining Ar-Ar data acquired on Martian meteorites, and others can be evaluated through numerical modeling of simulated K-Ar isochrons like those that would be acquired robotically on Martian rocks. Excess 40Ar is present in all shergottites. Thus for Martian rocks, the slopes of K-Ar isochrons must be determined to reasonable precision in order to calculate reliable ages. Model simulations of possible isochrons give an indication of some requirements in order to define a precise rock age: Issues addressed here are: how many K-Ar analyses should be made of rocks thought to have the same age; what range of K concentrations should these analyzed samples have; and what analytical uncertainty in K-Ar measurements is desirable. Meteorite data also are used to determine the D/a^2 diffusion parameters for Ar in plagioclase and pyroxene separates of several shergottites and nakhlites. These data indicate the required temperatures and times for heating similar Martian rocks in order to extract Ar. Quantitatively extracting radiogenic 40Ar could be difficult, and degassing cosmogenic Ar from mafic phases even more so. Considering all these factors, robotic K-Ar dating of Martian rocks may be achievable, but will be challenging.