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Title: THE TAGISH LAKE METEORITE FALL: INTERPRETATION OF FIREBALL PHYSICAL CHARACTERISTICS

Abstract

No abstract prepared.

Authors:
;
Publication Date:
Research Org.:
Los Alamos National Lab., NM (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
788213
Report Number(s):
LA-UR-01-5654
TRN: US200306%%174
DOE Contract Number:
W-7405-ENG-36
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Oct 2001
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; METEORITES; PHYSICAL PROPERTIES; LANL

Citation Formats

P. G. BROWN, and D. O. REVELLE. THE TAGISH LAKE METEORITE FALL: INTERPRETATION OF FIREBALL PHYSICAL CHARACTERISTICS. United States: N. p., 2001. Web.
P. G. BROWN, & D. O. REVELLE. THE TAGISH LAKE METEORITE FALL: INTERPRETATION OF FIREBALL PHYSICAL CHARACTERISTICS. United States.
P. G. BROWN, and D. O. REVELLE. Mon . "THE TAGISH LAKE METEORITE FALL: INTERPRETATION OF FIREBALL PHYSICAL CHARACTERISTICS". United States. doi:. https://www.osti.gov/servlets/purl/788213.
@article{osti_788213,
title = {THE TAGISH LAKE METEORITE FALL: INTERPRETATION OF FIREBALL PHYSICAL CHARACTERISTICS},
author = {P. G. BROWN and D. O. REVELLE},
abstractNote = {No abstract prepared.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Oct 01 00:00:00 EDT 2001},
month = {Mon Oct 01 00:00:00 EDT 2001}
}

Conference:
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  • We have analyzed available instrumental and eyewitness records associated with the fireball leading to the fall of the Tagish Lake meteorite. Initial chemical and physical studies of this carbonaceous chondrite have shown it to be unique. It is one of the most primitive meteorites yet recovered and extremely friable. By determining the original bodies trajectory, velocity and physical breakup in the atmosphere we can characterise the fireball as intermediate between Type II and Type IIIa, following the classification of Ceplecha et al. Modelling of the object suggests an initial porosity of the pre-atmospheric body in the range 40-60%. The initialmore » fragmentation occurred under less than 0.3 MPa dynamic pressure. Determination of Tagish Lake's orbit suggests a nominal linkage to parent bodies in the main asteroid belt, though association with short-period comets cannot be strictly excluded. It is suggested that Tagish Lake represents an intermediate object between chondritic asteroids and cometary bodies and our results are consistent with a linkage to D-class asteroids based on results from reflectance-spectra work.« less
  • The Tagish Lake C2 (ungrouped) carbonaceous chondrite fall of January 18, 2000 delivered >10 kg of one of the most primitive and physically weak meteorites yet studied. In this paper we report the detailed circumstances of the fall and the recovery of all documented Tagish Lake fragments. We also provide measurements of bulk physical properties (mass, grain and bulk density), bulk triple oxygen-isotope ratios, and short-lived cosmogenic radionuclides counts for several fragments. Ground eyewitnesses and recorded observations of the Tagish Lake fireball event provide a refined estimate of the fireball trajectory, and hence, its pre-atmospheric orbit. From its calculated orbitmore » and its similarity to the remotely-sensed properties of the D and P-class asteroids, the Tagish Lake carbonaceous chondrite represents these outer belt asteroids, and is not of cometary origin. The bulk oxygen-isotope compositions reported here are among the highest known for meteorites. These data plot just below the Terrestrial Fractionation Line, following a trend similar to the CM meteorite mixing line. The bulk density of the Tagish Lake material (1.66 ±0.02 g/cm3) is the same, within error, as the total bulk densities of many C-class and especially D- and P-class asteroids. The high microporosity of Tagish Lake samples (~40%) provides an obvious candidate material for the composition of low bulk density primitive asteroids such as Phobos, Deimos and the P-class binary 87 Sylvia, without requiring a substantial contribution from macroporosity in the form of ice, thick regolith or “rubble pile” assemblages with large interior voids.« less
  • Quantitative electric-log interpretation, using multiple log responses, can be used as a tool to identify Fall River point-bar reservoirs. Many authors have shown how SP curve shapes can be used to identify point bar and fluvial deposits. However, few have attempted to characterize and identify point-bar deposits through quantitative and qualitative interpretation using several electric-log responses in combination. Multiple log response are used to identify the sharp basal contact, high permeability, and larger grain size typical in the lower portion of Fall River Point-bar deposits, and the gradation into finer grain size and lower permeabilities typical in upper portions. Themore » techniques works best in producing wells that are at irreducible water saturation. In these, porosity can be plotted vs. water saturation, and relative estimates of vertical grain size changes can be determined. Gamma-ray and density logs are unitized to aid in identifying the narrow, channel filling clay plugs associated with point bars. Reservoirs from two fields in the Powder River basin demonstrate the technique. One field includes reservoir rocks interpreted in several ways by previous authors. The second is a more recent Dakota Third Bench reservoir in the Lonetree Creek field, where many of the techniques applied in this study were developed. Observation of porosity and resistivity development in vertical sequence, and the position on porosity and water saturation crossplots are used to aid in distinguishing between regional depositional environment, point-bar deposits, and channel fill.« less
  • We report a coordinated analytical study of matrix material in the Tagish Lake carbonaceous chondrite in which the same small ({le}20 {micro}m) fragments were measured by secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), electron energy-loss spectroscopy (EELS), and X-ray absorption near-edge spectroscopy (XANES). SIMS analysis reveals H and N isotopic anomalies (hotspots), ranging from hundreds to thousands of nanometers in size, which are present throughout the fragments. Although the differences in spatial resolution of the SIMS techniques we have used introduce some uncertainty into the exact location of the hotspots, in general, the Hmore » and N isotopic anomalies are spatially correlated with C enrichments, suggesting an organic carrier. TEM analysis, enabled by site-specific extraction using a focused-ion-beam scanning-electron microscope, shows that the hotspots contain an amorphous component, Fe-Ni sulfides, serpentine, and mixed-cation carbonates. TEM imaging reveals that the amorphous component occurs in solid and porous forms, EDS indicates that it contains abundant C, and EELS and XANES at the C K edge reveal that it is largely aromatic. This amorphous component is probably macromolecular C, likely the carrier of the isotopic anomalies, and similar to the material extracted from bulk samples as insoluble organic matter. However, given the large sizes of some of the hotspots, the disparity in spatial resolution among the various techniques employed in our study, and the phases with which they are associated, we cannot entirely rule out that some of the isotopic anomalies are carried by inorganic material, e.g., sheet silicates. The isotopic composition of the organic matter points to an initially primitive origin, quite possibly within cold interstellar clouds or the outer reaches of the solar protoplanetary disk. The association of organic material with secondary phases, e.g., serpentine and carbonates, suggests that the organic matter was susceptible to parent-body processing, and thus, isotopic dilution.« less