Black, magnetic spherules in sediments

Crozier, W. D.

doi:10.1029/jz065i009p02971

Cited by 55 publications

(19 citation statements)

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“…The atmospheric spherules discussed in this and the 1962 paper appear to be similar to those which I have collected from various sedimentary rocks [Crozier, 1960] and to those collected by other investigators. Especially noteworthy are the collections from antarctic ice [Thiel and Schmidt, 1961;Schmidt, 1963], from Greenland ice [Langway, in preparation], and from certain salt deposits [M'utch, 1964].…”

supporting

confidence: 83%

Nine years of continuous collection of black, magnetic spherules from the atmosphere

Crozier¹

1966

J. Geophys. Res.

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Data on the deposition of black, magnetic spherules from the atmosphere, at two stations in central New Mexico, have accumulated for the 9‐year period 1956–1964. These spherules, which appear to be similar to those which I have recovered from various sedimentary rocks and to those recovered by others from ice in Antarctica and Greenland and from Paleozoic salts, are believed to be of extraterrestrial origin. The 9‐year average of the annual rate of mass accretion to the earth, for spherules in the diameter range of 5 to 60 μ, was approximately 1.04×1011 grams. The period included 2 years in which the annual infall was nearly 2.5×1011 grams, however, and therefore the long‐term average remains somewhat uncertain. The size distributions show fluctuations but, in general, are similar to those previously reported. The rate of deposition decreased from 1956 to 1962, and high peaks occasionally occurred. Interesting seasonal and biennial patterns appear in the rate of deposition, and there seems to be a degree of correlation between the spherule rates and radar meteor rates, the spherule rates leading the radar rates by about 6 weeks. In 1963, high rates of spherule deposition coincided with unusually high radar meteor rates.

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confidence: 83%

Nine years of continuous collection of black, magnetic spherules from the atmosphere

Crozier¹

1966

J. Geophys. Res.

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“…We interpret our smaller daily influx rate as evidence that above 100 km a significant fraction of the particles in the size range 0.3 MO<3 M are in geocentric, quasiclosed orbits. This hypothesis is strengthened by the agreement of our estimates with the rate of approximately 10* metric tons per year for meteoric dust settling through the air or deposited on the ground (Crozier, 1960;Laevastu and M ell is, 1961;Pettersson, 1960;Crozier, 1961;Crozier, 1962;Wright and Hodge, 1962). An alternate explanation is that the majority of meteoric particles are too fragile to survive passage through the atmosphere.…”

Section: Height (Thousands Of Feet)supporting

confidence: 69%

Meteor orbits and dust; the proceedings of a symposium

Hawkins¹

1967

Smithsonian Contributions to Astrophysics

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The Proceedings of the Symposium on Meteor Orbit* and Dust is published simultaneously as a NASA Special Publication (SP-135) and as Volume 11 of the Smithsonian Contributions to Astrophysics. This single publication thus serves in a dual capacity to satisfy the requirements of both agencies for the published record of this international meeting.The NASA Special Publications series, begun in 1962, makes available information derived from or of value to NASA activities, and includes such publications as conference proceedings, monographs, data compilations, handbooks, Bourcebooks, and special bibliographies.The IntroductionWe recently completed a general analysis of the atmospheric trajectories of 413 precisely reduced Super-Schmidt photographic meteors (Jacchia, Verniani, and Briggs, 1965). We studied the dependence of heights, lengths, decelerations, and magnitudes on such basic parameters as velocity, angle of incidence, and mass, as well as on derived parameters such as the ablation coefficient and the fragmentation index; the latter were in turn related to the other geometrical and physical characteristics, including the phenomena of wake and terminal blending. The results of the analysis are mainly concerned with physical characteristics of meteors; in this paper we shall limit ourselves to only a few points related to problems of orbits and distribution, namely, physical differences dependent on the type of orbit, peculiarities of individual showers, and the mass scale for photographic meteors.Systematic differences between groups of meteors Systematic differences in some physical characteristics between meteors in short-period and long-period orbits were first pointed out by Jacchia (1958Jacchia ( , 1963. He found that the beginning heights of meteors with aphelion distances greater than 7 a.u. were higher than the corresponding heights of meteors with aphelion distances smaller than 7 a.u. All meteors were, of course, reduced to the same brightness.• Smithsonian Astrophysical Observatory and Harvard College Observatory, Cambridge, Massachusetts.'Smithsonian Astrophysical Observatory and Harvard College Observatory; on leave from Centra Nationals per la Fisica dell'Atmosfera c la Meteorologia del C.N.R., Rome, Italy. * Smithsonian Astrophysical Observatory, Cambridge, Massachusetts.The present general analysis has confirmed the effect found by Jacchia: meteors with aphelion distance smaller than 6 a.u. appear 1.8 km lower than meteors in long-period orbits, reduced to the same velocity, mass, and zenith angle. The maximum light and end heights are correspondingly lower ( fig. 1). This effect is related to the different densities that we find for the two groups: on the average, meteors in short-period orbits appear to be about 1.4 times as dense as meteors in long-period orbits. In addition, for short-period meteors, the density increases as the aphelion distance decreases ( fig. 2). These systematic differences in density could be ascribed to the different conditions in which the meteoroids were formed ...

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“…Until recently, our Itnowledge of micrometeoroids was derived from observations of the zodiacal light (Blackwell and Ingham 1961) and the noctilucent clouds (Bronshten et al 1963), from particle collection in the atmosphere (Hodge and Wildt 1958;I-Iodge and Wright 1962), and from the examination of land sediments (Crozier 1960) and deep-sea deposits (Petterson and Fredriksson 1958). With the development of sounding and satellite-launching rockets, new research tools became available.…”

mentioning

confidence: 99%

Detecting Micrometeoroids Acoustically From Rockets

Wlochowicz¹

1966

Can. J. Phys.

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Two models of acoustic micrometeoroid detectors were flown piggyback on several Canadian rockets, one of which was launched in the spring of 1963 and the others in the winter and fall of 1964 from the Churchill Rocket Range. The micrometeoroid detecting systems and the calibration technique based on the elastic impact of polystyrene spheres are described. The detector response is found to be proportional to m0.8vl.l. Responses recorded during six flights are presented and analyzed. The analysis is developed in detail to illustrate the uncertainties in interpreting the data and to establish qualitatively the accuracy of the results. Responses attributed to impacts of micrometeoroids are treated collectively. An average impact rate of 1.4/mz sec and a threshold mass of 10-11 g a t 30 km/sec are ascribed to the data. A high density of small particles is apparently indicated. Impact rates for successive 5-km intervals to a height of 167 km indicate a variation with height. Regions of increased activity, roughly double the average rate, are observed centered on the height intervals 145 to 150 km and 125 to 130 km. A region of slightly less activity exists near 90 km, and a sharply defined region appears a t the 105 to 110 km interval. T h e relative stability of all or any of these active regions has yet to be established.

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Black, magnetic spherules in sediments

Cited by 55 publications

References 5 publications

Nine years of continuous collection of black, magnetic spherules from the atmosphere

Nine years of continuous collection of black, magnetic spherules from the atmosphere

Meteor orbits and dust; the proceedings of a symposium

Detecting Micrometeoroids Acoustically From Rockets

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