In previous studies, intersample variation between compositions of different tektites from one particular group were studied and, in a few cases, major element variations within single tektites. No data for intra-sample trace element variations existed. Thus, we sectioned a Muong Nong-type tektite fragment from Vietnam and a splash-form tektite fragment from the Philippines into eleven and six pieces, respectively, and analyzed the individual fragments for major and trace element contents.The compositions obtained agree well with those found in previous studies, supporting argument that tektites have been derived from terrestrial upper crustal sediments. Chemical variations within the tektite fragments are present, but do not show any systematic trends, probably reflecting incomplete mixing of parent rocks. The intra-sample heterogeneity of the Muong Nong-type tektite is more pronounced than that in the philippinite. For the Muong Nong-type tektite, the intra-sample variation in the trace element contents is higher than that for the major elements, again reflecting target rock properties. For the philippinite the intra-sample variations mostly do not exceed the limits imposed by the precision of the analytical data, confirming that the splash form tektites are indeed well homogenized.

We have investigated the texture, bulk chemistry, mineralogy, as well as the anhydrous minerals oxygen isotopic composition of 67 small Antarctic micrometeorites (AMMs) collected at Cap Prudhomme, Antarctica, and belonging to the currently poorly studied size fraction 25-50 micrometers. When compared to larger (50-400 micrometers) micrometeorites collected at the same site in Antarctica with the same techniques, no significant differences are found between the two populations. We therefore conclude that the population of Cap Prudhomme AMMs is homogeneous over the size range 25-400 micrometers. In contrast, small AMMs have different textures, mineralogy, and oxygen isotopic compositions than those of stratospheric interplanetary dust particles (IDPs). Because small AMMs (<50 micrometers) overlap in size with IDPs, the differences between these two important sources of micrometeorites can no longer be attributed to a variation of the micrometeorite composition with size. Physical biases introduced by the collection procedures might account for these differences.

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 entryparameters, 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-downbottom-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.

The rocks exposed in the rim of the 2.5-km-wide and 3.7-Ma-old Roter Kamm crater in southwest Namibia are cut by breccia veins that macroscopically resemble, and were originally described as, pseudotachylytes. The veins were later shown to be cataclasites with no evidence for melting. 40Ar/39Ar data for vein and host rock samples indicate a low-grade metamorphic event at around 300 Ma, but provide no evidence for an impact age. The samples have suffered 5-7% Ar loss, which we associate with the impact event. All the samples record similar ranges of possible timetemperature conditions and there are no resolvable differences between the results for the vein and the host rock samples, as would be expected if frictional heating played an important role in breccia formation. Modeling the 40Ar/39Ar data, assuming instantaneous impact heating followed by extended cooling, and coupling these results to published data on fluid inclusions, quartz precipitation, shock effects, and crater degradation, suggest that the veins reached maximum temperatures of 230-290 degrees C during impact and never approached melting temperatures of the precursor rocks.

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 x 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.