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The effects of micrometeorite impact on the optical properties of metals
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Development of experimental and statistical methods for obtaining and interpreting micrometeorite data from space vehicles Semiannual status report, 1 Aug. 1965 - 31 Jan. 1966
Construction and calibration of capacitor microphones for cosmic dust detection
Techniques for the observation of micrometeorite craters in metal substrates utilizing electron micrographic replica methods
Thin film replica technique for obtaining high quality electron micrographs of craters in metal substrates formed by microscopic hypervelocity particle impact
Experiment S010 /S-10/, Agena micrometeorite collection
Recorded micrometeoroid impacts on Agena mounted polished plates recovered during Gemini docking
Experiment S012 /S-12/, micrometeorite collection
Determination of meteorite activity outside Gemini 10 spacecraft by exposed metal plate
Contaminants vs micrometeorites from the 1965 Leonid meteor shower
Separation and identification of contaminants found on collecting surfaces exposed to Leonid meteoroid shower in 1965
Activation analysis for selected elements in micrometeorites and hypervelocity projectiles Annual progress report, 1 Jul. 1969 - 1 Jul. 1970
Activation analysis to identify materials for use as catcher for micrometeoroids
The Manned Spacecraft Center Gemini micrometeorite collection experiment
Micrometeoroid impact experiments conducted on Gemini 9 and 12 missions
Micrometeorite craters and related features on lunar rock surfaces
Microcraters on Apollo 12 crystalline rocks and breccia surfaces attributed to primary cosmic particles
Micrometeorite craters on lunar glass particles - The relationship between radial fracture zones and spall zones.
Discussion of the microimpact-crater morphology observed by scanning electron microscopy on a glass bead (nearly 580 microns in maximum diameter) recovered from zone A of the Luna 16 sample. The microcrater has a diameter of approximately 200 microns and a centrally located melted region or pit that is slightly elevated above the surrounding area. Around the pit is a radial fracture zone half of which has spalled off. The spall zone is more than half again as large as the radial fracture zone.
S-149 micrometeorite collection experiment
There are no author-identified significant results in this report.
Micrometeorites and solar flare particles in and out of the ecliptic
Using crystals grown into vugs from oriented lunar rocks as directional detectors of cosmic dust particles and solar flare nuclei, I have measured the angular distribution of the flux of micrometeoroids of mass 30 attograms to 80 femtograms. Hypervelocity impact craters of diameter 500 A to 10 microns and tracks from solar flare nuclei of energy 100 keV/amu to 20 MeV/amu were observed in crystals from rock 71055 facing lunar south and in crystals from rock 74255 facing lunar east. I have found that dust grains both in ecliptic orbits and in orbits inclined to the ecliptic have virtually identical mass-frequency distributions and similar shapes. I have evaluated the micrometeoroid fluxes after determining the exposure ages of the individual vug crystals by measuring the solar flare track density gradients in each crystal. The flux of particles of mass greater than 4 femtograms confined to the ecliptic is in good agreement with satellite measurements, suggesting that the micrometeoroid flux has been relatively constant over the past 35,000 yr. The flux of particles producing microcraters on a lunar surface facing south is lower than the ecliptic flux by a factor of about 7.
Comment on 'Micrometeorites and solar flare particles in and out of the ecliptic' by I. D. Hutcheon
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Ferromagnetic resonance as a method of studying the micrometeorite bombardment history of the lunar surface
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The importance of capturing unmodified chondritic porous micrometeorites on the space station
The survival of interplanetary dust particles (IDP's) during deceleration by the Earth's atmosphere is determined by their entry parameters, velocity, size and mass. These IDP's reach their terminal velocity at about 55 to 95 km altitude before they gradually settle to 18 to 21 km altitude where they are collected by high flying aircraft. Chondritic porous IDP's (also called chondritic porous (CP) aggregates) show properties consistent with an extraterrestrial origin. It is conceivable that CP aggregates may be collected above the Earth's atmosphere using capture devices on a space station or satellite. In order to preserve pristine CP aggregates, i.e., aggregates with minimal perturbation or degradation of its particulate matter, it is necessary to transfer the kinetic energy on impact so that a minimum amount of energy is dissipated into the impacting particle. It is likely that low-temperature minerals (e.g., layer silicates), volatile phases (e.g., sulfides), structural defects (e.g. nuclear tracks) and hydrocarbons in CP aggregates are sensitive to the efficiency of kinetic energy dissipation.
Atmospheric entry heating of micrometeorites
A computer simulation of the atmospheric entry deceleration and heating of cosmic dust particles has been developed and the predicted peak temperatures are compared to the earlier closed-form mathematical solutions of Whipple (195) and Fraundorf (1980). A 20-micron diameter particle of density 1 gm/cu cm having a velocity of 10 km/s at infinity and entering the atmosphere at normal incidence reaches a peak temperature of 1159 K. The duration of the heating pulse is about 8 s but the particle remains within 100 K of the peak temperature for only 1.0 s. As the angle of incidence decreases, the peak temperature reached on entry also decreases, and the duration of the temperature pulse increases. Comparison with the Whipple amd Fraundorf models indicates that they accurately assess the entry heating for cosmic dust particles of moderate or higher densities and entry angles near normal incidence. As particle density decreases or the entry angle nears grazing incidence, they overestimate the peak temperature.
Major element composition of stratospheric micrometeorites
Results are presented on an element-composition study conducted on 200 interplanetary dust particles (IDPs) collected with NASA's U2 and RB 47 aircraft at altitudes near 20 km. These IDPs could be classified into two major morphological types, i.e., the 'porous' and the 'smooth' particle types, which showed significant compositional differences. Namely, elemental abundances found in porous particles are closely matching those of the CI chondrites, while the smooth particle group displayed systematic Ca and Mg depletions and contained stoichiometric 'excess' oxygen, consistent with the presence of hydrous phases. This fact, together with the occurrence of carbonates, magnetite framboids, and layer silicates, provides evidence that at least a significant number of the smooth-type IDPs were processed by aqueous activity. It is hypothesized that extensive aqueous activity only occurs in asteroids (as opposed to comets) and that the smooth class of IDPs is of an asteroidal origin.