Search NASA⌕ Search

SEARCH · Search NASA

Results for “micrometeorites”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Experiment S012: Micrometeorite collection

The micrometeorite activity in a near-earth environment and the effect of the environment on microorganisms were studied by exposure of polished metal and plastic surfaces to the environment outside the Gemini spacecraft. Preliminary results are summarized as follows: (1) The cumulative influx rate in the size ranges from 10 to the minus 15th power to 10 to the minus 14th power gram was approximately 2 particles/ sq m/sec, as determined on the Gemini 12 mission; (2) The cumulative influx rate in the same mass range, as determined by the data from the Gemini 9 mission was almost 200 particles/ sq m/sec; and (3) The large particle cumulative influx rate was about 3 x 0.00001 particle/ sq m/sec, with a mass of the order of 10 to the minus 7th power gram. No living organisms could be found on the sterile collecting surfaces after recovery and handling.

Hemenway, C. L.↗
NASA NTRS1974

Solar wind and micrometeorite alteration of the lunar regolith

Developments in the understanding of reduction processes which occur in the lunar regolith as a result of solar-wind bombardment and micrometeorite impacts are discussed. The mechanism is described by which water released during reduction is removed from the lunar surface, and the possible contribution of solar-wind sputtering to the reduction process is considered. It is shown that the overall reduction efficiency of incoming hydrogen ions may reach several per cent, which is sufficient to produce all the metallic iron observed in the regolith. Mossbauer spectroscopic data on the amount of metallic iron present as isolated atoms or small clusters in reduced grain surfaces are presented together with data on the metallic iron content of fines samples obtained by Mossbauer spectroscopy, ferromagnetic resonance, and scanning as well as transmission electron microscopy. A portable magnetic probe is described which has been designed for determining surface-exposure age profiles in intact lunar core and drive-tube samples.

Housley, R. M.↗
NASA NTRS1976

Micrometeorite penetration effects in gold foil

Penetration structures revealed by a Skylab experiment dealing with exposure of single and double layers of 500-800 A thick gold foil to micrometeorites are examined. Examination of all double-layered gold foils revealed that particles producing holes of any type greater than 5 microns in diameter in the first foil break up into many fragments which in turn produce many more holes in the second foil. Evidence of an original particle is not found on any stainless steel plate below the foils, except in one instance. A precise relationship between the size of the event and the mass of the particle producing it could not be determined due to the extreme morphological variety in penetration effects. Fluxes from gold foil and crater experiments are briefly discussed.

Hallgren, D. S.↗
NASA NTRS1977

Solar wind and micrometeorite effects in the lunar regolith

Using available data from the literature, an outline is formulated for the major physical and chemical effects expected during solar-wind bombardment of the lunar regolith. In agreement with results of Auger and other analyses of the composition of lunar grain surfaces, this outline predicts that solar-wind sputtering will tend to clean exposed grain surfaces by ejecting material at velocities exceeding lunar escape velocity. Results are also discussed which show that Fe is partially reduced in the outer few 10 nm of grain surfaces and that this reduced Fe forms 10-nm-diameter metal spheres throughout the glass during agglutinate formation by micrometeorite impacts. These metal spheres give the agglutinates their distinctive optical and magnetic properties and are partially responsible for the decreasing albedo of the lunar surface with exposure age.

Housley, R. M.↗
NASA NTRS1980

The distribution of temperature maxima for micrometeorites decelerated in the earth's atmosphere without melting

A simple model for the statistics of heating of micrometeorites decelerated in the earth's atmosphere without melting predicts that for 10 micron particles with thermal emissivity near 1, roughly half of those with density 1 g/cc are heated above 550 C, while half of those with density 3 g/cc are heated above 800 C. In the study of stratosphere collected interplanetary dust, the model can be helpful in identifying petrographic thermometers of the atmospheric entry process, and in understanding the most recent history of this new class of extraterrestrial material available in the laboratory.

Fraundorf, P.↗
NASA NTRS1986

Trajectory determinations and collection of micrometeoroids on the space station. Report of the Workshop on Micrometeorite Capture Experiments

Summaries of papers presented at the Workshop on Micrometeorite Capture Experiments are compiled. The goals of the workshop were to define the scientific objectives and the resulting performance requirements of a potential Space Station facility and to identify the major elements of a coherent development program that would generate the desired capabilities within the next decade. Specific topics include cosmic dust and space debris collection techniques, particle trajectory and source determination, and specimen analysis methods.

Hoerz, F.↗