Ultrathin Amorphous Coatings on Lunar Dust Grains

Bibring, J. P.; Duraud, J. P.; Durrieu, L.; Jouret, C.; Maurette, M.; Meunier, R.

doi:10.1126/science.175.4023.753

Cited by 58 publications

(37 citation statements)

References 15 publications

(10 reference statements)

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“…A distinctive microscopic feature of lunar soil grains was discovered soon after the return of the first Apollo samples, when high-voltage transmission electron microscope (HVTEM) observations showed that many soil grains were surrounded by thin amorphous rims (e.g., Dran et al, 1970;Bibring et al, 1972). These results, when combined with laboratory experiments on artificially irradiated grains, demonstrated that amorphous rims could form in response to the implantation of ions with solar wind energies.…”

Section: Introductionsupporting

confidence: 51%

The nature and origin of rims on lunar soil grains

Keller¹,

McKay²

1997

Geochimica et Cosmochimica Acta

343

284

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Abstract-Spaceweathering processes that operate in the lunar regolith modify the surfaces of lunar soil grains. Transmission electron microscope analysis of the lunar soil grains from the fine size fraction of several lunar soils show that most grains are surrounded by thin nm thick) rims. The microstructure and chemical compositions of the rims can be used to classify rims into four broad categories: amorphous, inclusion-rich, multiple, and vesicular. Amorphous rims are noncrystalline, generally lack crystalline inclusions, show evidence for preferential sputtering of cations, and are produced largely by solar-wind irradiation damage. Inclusion-rich rims contain abundant nanometer-sized grains of Fe metal as randomly dispersed inclusions or as distinct layers embedded in an amorphous silica-rich matrix. Inclusion-rich rims are compositionally distinct from their host grains and typically contain accumulations of elements that are not indigenous to the host. Inclusion-rich rims are formed largely by the deposition of impact-generated vapors with a contribution from the deposition of sputtered ions. A continuum in the chemical and microstructuralproperties exists between typical amorphous rims and typical inclusion-rich rims. Multiple-rims consist of a distinct radiation-damaged layer up to SO nm thick, that is overlain by vapor-deposited material of comparable thickness. Vesicular rims are compositionally similar to their hosts and are characterized by an abundance of small (<50 nm in diameter) vesicles concentrated in the outer 100 nm of the rims. The formation of vesicular rims is apparently due to the evolution of solar-wind implanted gases in response to a pulse-heating event. The formation of rims on lunar soils is complex and involves several processes whose effects may be superimposed.From this study, it is shown that one process does not dominate and that the relative importance of vapor-deposition is comparable to radiation-damage in the formation of rims on lunar silicate grains. The presence of rims on lunar soil grains, particularly those with nanometer-sized Fe metal inclusions, may have a major influence on the optical and magnetic properties of lunar soils.

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Section: Introductionsupporting

confidence: 51%

The nature and origin of rims on lunar soil grains

Keller¹,

McKay²

1997

Geochimica et Cosmochimica Acta

343

284

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“…Early transmission electron microscope (TEM) observations revealed that regolith silicates have amorphous surface layers with thicknesses and microstructures similar to those found in experimentally irradiated analog materials (Dran et al, 1970;Bibring et al, 1972Bibring et al, , 1974Bibring et al, , 1975Borg et al, 1980Borg et al, , 1983. The chemical composition of the surface of natural regolith grains as determined by Auger, x-ray photoelectron, and secondary-ion spectroscopies was also seen as generally consistent with solar radiation effects (Yin et al, 1975a(Yin et al, , b, 1976Housley andGrant, 1975, 1976;Gold et al, 1975;Zinner et al, 1976).…”

Section: Introductionmentioning

confidence: 78%

“…The last mechanism above is based on measurements which show that radiant heating raises the top 1-2 cm of the lunar soil to 100-130°C for 5-7 d during the lunar daytime (Langseth et al, 1973;Mendell, 1976). Although such temperatures are relatively low, the duration of heating integrated over the estimated 5000-150,000 year surface residence time for small regolith grains (Duraud et aL, 1975;Borg et al, 1976) et al, 1970;Bibring et al, 1972Bibring et al, , 1974Bibring et al, , 1975Borg et al, 1980Borg et al, , 1983. The inner layer is not easily explained by heating effects alone, and solar ion radiation effects are therefore left as an alternative.…”

Section: Formation Of the Outer Rim Layermentioning

confidence: 99%

Microstructure, chemistry, and origin of grain rims on ilmenite from the lunar soil finest fraction

Christoffersen

McKay

Keller³

1996

Meteorit & Planetary Scien

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“…Until the recent return of the Hayabusa mission from S-type asteroid Itokawa , samplebased studies of space weathering focused exclusively on lunar soils returned from the Apollo missions and select asteroidal and lunar regolith breccia meteorites (Bibring et al 1972;Hapke et al 1975;McKay 1993, 1997;Bernatowicz et al 1994;Pieters et al 2000;Taylor et al 2001;Noble et al 2005Noble et al , 2011. These investigations indicated that space weathering features form as a product of two primary processes: (i) solar wind ion irradiation, which can cause partial or complete amorphization of material and possible chemical changes in grain rims, as well as erosion, transport, and redeposition of material on grain surfaces induced by ion sputtering, and (ii) micrometeorite impact events which promote melting, vaporization, and the recondensation of the target and impactor material.…”

Section: Introductionmentioning

confidence: 99%

Microchemical and structural evidence for space weathering in soils from asteroid Itokawa

et al. 2014

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Here we report microchemical and microstructural features indicative of space weathering in a particle returned from the surface of asteroid Itokawa by the Hayabusa mission. Space weathering features include partially and completely amorphous rims, chemically and structurally heterogeneous multilayer rims, amorphous surface islands, vesiculated rim textures, and nanophase iron particles. Solar-wind irradiation is likely responsible for the amorphization as well as the associated vesiculation of grain rims. The multilayer rims contain a nanocrystalline outer layer that is underlain by an amorphous inner layer, and both have compositions that are distinct from the underlying, crystalline orthopyroxene grain. The multilayer rim features could be derived from either radiation-induced sputter deposition or vapor deposition from micrometeorite impact events. The amorphous islands on grain surfaces have a distinctive morphology and composition suggesting that they represent surface deposits of melt derived from micrometeorite impact events. These observations indicate that both irradiation damage and micrometeorite impacts play a role in surface modification and space weathering on asteroid Itokawa.

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Ultrathin Amorphous Coatings on Lunar Dust Grains

Cited by 58 publications

References 15 publications

The nature and origin of rims on lunar soil grains

The nature and origin of rims on lunar soil grains

Microstructure, chemistry, and origin of grain rims on ilmenite from the lunar soil finest fraction

Microchemical and structural evidence for space weathering in soils from asteroid Itokawa

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