The Solar Irradiation Record in Lunar Dust Grains

Abstract Properties of cometary dust particles are better known since the space missions to Comet Halley. Their properties (densities, atomic composition) are compared with relevant observations from lunar microcraters and in-situ experiments. At 1 AU in the eliptic, 2/3 of the dust grains are normal density particles, presumably of asteroidal origin and irregularly shaped, while the remaining 1/3 are low density particles, presumably of cometary origin, but due to solar irradiation in a processed state (corresponding to “Brownlee”-particles). Beyond the asteroidal belt only black cometary dust grains are observed which have recently been released from comet nuclei orbiting on highly eccentric trajectories.

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Reflection Spectra of Lunar Dust Grains with Amorphous Coatings

Science ◽

10.1126/science.177.4048.535 ◽

1972 ◽

Vol 177 (4048) ◽

pp. 535-536 ◽

Cited By ~ 2

Author(s):

B. Hapke

Keyword(s):

Reflection Spectra ◽

Dust Grains ◽

Lunar Dust ◽

Amorphous Coatings

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The Solar Irradiation Record in Lunar Dust Grains

Symposium - International Astronomical Union ◽

10.1017/s0074180900097618 ◽

1972 ◽

Vol 47 ◽

pp. 298-308

Author(s):

J. Borg ◽

B. Vassent

Keyword(s):

External Surface ◽

Lunar Soil ◽

Solar Irradiation ◽

Solar Cosmic Rays ◽

Core Tube ◽

Transmission Microscopy ◽

Lunar Dust ◽

Electron Microscopies ◽

The Core ◽

Different Depths

Comparative studies of the distribution of latent and etched tracks in lunar grains from five different size fractions of three lunar fine samples and of six lunar dust samples taken at different depths in core tube 12028 have been performed by using transmission and scanning electron microscopies. Two very different sets of etching conditions were used: a slight etching was applied for transmission microscopy but a much stronger etching was used for scanning microscopy. We observed: (1) a definite stratigraphy in the core tube, both in the latent and etched track distributions; (2) striking differences between the densities of the latent and slightly etched tracks (≥ 1010 tracks cm−2) and those of the strongly etched tracks, ranging from ⋍ 108 to 5.109 tracks cm−2; (3) a lack of correlation between the grain size and the density of strongly etched tracks observed on the external surface of grains from sample 12032; (4) no variation of the density of the tracks with the depth inside a grain. Some implications of the present results concerning the ancient low energy solar cosmic rays and the fabric of the lunar soil will be briefly discussed.

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