An interpretation of historical records of aurorae and meteors in Chinaduring the 11th and 12th centuries A.D.: Possible indications ofaccretion of interstellar medium?

More than 5000 meteors were recorded in ancient Chinese chronicles. The frequency of meteor sighting shows an anomalous increase during the 11th century A. D. This seems to be consistent with the inference that the solar system encountered a small molecular cloud, although KEIMATSU et al. (J. Geomagn. Geoelectr., 20,45,1968) suggested that the geomagnetic dipole axis could have been inclined towards China around the 11th century based on historical records of aurorae and sunspots

Terrestrial ages of the Antarctic meteorites measured by thermoluminescence of the fusion crust: II

The acquired doses of Antarctic meteorites for dating of terrestrial ages were measured by the thermoluminescence (TL) intensity of fusion crust. It is now clearer that there is a significant correlation between the acquired dose and terrestrial age, which was previously measured by cosmogenic radionuclide abundance. Also, the ^Cl method by accelerator mass spectrometry seems to provide a large terrestrial age occasionally

PIXE analysis of magnetic spherules in Paleozoic-Mesozoic bedded chert

Particle Induced X-ray Emission (PIXE) was applied to the elemental characterization of magnetic microspherules collected from the Paleozoic and Mesozoic bedded chert in Southwest Japan. Comparison of the titanium and chromium contents of the spherules with the magnetic components of meteorites and volcanic ash showed that this technique offers promising potential as a new method for distinguishing between spherules of terrestrial and extraterrestrial origin

Magnetic microsperules in Permian and Triassic bedded chert from Southwest Japan

Magnetic microspherules collected from the Permian and Triassic bedded cherts in Southwest Japan were studied. The size range, as estimated from 801 microspherules, vary from 3 to 100μm, with a peak size distribution between 10-20μm. Three broad shapes are recognized : spherical-, drop- and rocket-shaped, all categories including hollow particles. The surface textures as studied from scanning electron microscope show five dominant varieties : random mosaic, dendritic mosaic, feather crystal, scaly and cracked, with intermediate textures between these types. Chemical analyses of representative microspherules by electron microprobe indicate that they are mostly composed of magnetite, resembling in composition with microspherules of cosmic origin from other regions and magnetite grains in carbonaceous chondrites. Consideration of the origin of the observed morphologic, textural and chemical parameters in these microspherules, along with the available data on experimental synthesis of ultramicro iron particles, preclude an origin by volcanogenic processes and strongly suggest a cosmic origin. Knowledge of the rate of chert sedimentation allows us to make an empirical calculation on the rate of microspherule sedimentation. We compute that the fall of microspherules on the earth\u27s surface occurred at the rate of about 1 t/day during Permian, while it increased to about 3 t/day during the closing of the era and the Triassic

Terrestrial ages of Antarctic meteorites measured by thermoluminescence of the fusion crust

The acquired doses of 14 Antarctic meteorites were measured using the thermoluminescent (TL) intensity of the fusion crust. It was found that there is a good correlation between the acquired TL doses and the terrestrial ages, which were previously measured by the cosmogenic radionuclide abundance

Measurement of terrestrial age of Antarctic meteorites by thermoluminescence technique

The thermoluminescence (TL) of Antarctic meteorites, ALH-77256,90 (Di), ALH-77294,81,82 (H5), ALH-765,75,85 (Eu), ALH-768,83 (H6) and ALH-77272,83,84 (L6) is measured. The depth dependence of the TL for ALH-77294,81,ALH-765,75 and ALH-768,83,which have fusion crusts, is also measured. The heating of the surface material (0-1.5mm depth) during atmospheric passage is estimated from the fading of the high temperature TL. It is revealed that this atmospheric heating entirely removes the low temperature TL from the surface of a meteorite and the present low temperature TL glow of the surface material is produced by subsequent terrestrial radiation in Antarctica. The terrestrial ages of these meteorites are estimated from the TL of the surface material with an assumption about the Antarctic storage conditions (stored on the surface or buried under the ice sheet)