The oxidation state of nanophase Fe particles in lunar soil: Implications for space weathering

Thompson, M. S.; Zega, T. J.; Becerra, P.; Keane, J. T.; Byrne, Shane

doi:10.1111/maps.12646

Cited by 65 publications

(62 citation statements)

References 43 publications

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“…With high-resolution transmission electron microscopy (HRTEM), the interplanar spacing of the inclusions is measured in the high-resolution image as 0.204 nm (Figures 5b and 5c). This value is consistent with the interplanar spacing of (101) in α-Fe of 0.203 nm (Thompson et al, 2015).…”

Section: Tem Analysis Of the Irradiated Samplessupporting

confidence: 89%

Impact Characteristics of Different Rocks in a Pulsed Laser Irradiation Experiment: Simulation of Micrometeorite Bombardment on the Moon

Yao

et al. 2017

JGR Planets

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Without the protection of the atmosphere, the soils on lunar surfaces undergo a series of optical, physical, and chemical changes during micrometeorite bombardment. To simulate the micrometeorite bombardment process and analyze the impact characteristics, four types of rocks, including terrestrial basalt and anorthosite supposed to represent lunar rock, an H‐type chondrite (the Huaxi ordinary chondrite), and an iron meteorite (the Gebel Kamil iron meteorite) supposed to represent micrometeorite impactors, are irradiated by a nanosecond pulse laser in a high vacuum chamber. Based on laser irradiation experiments, the laser pits are found to be of different shapes and sizes which vary with the rock type. Many melt and vapor deposits are found on the mineral surfaces of all the samples, and nanophase iron (npFe) or Fe‐Ni alloy particles are typically distributed on the surfaces of ilmenite, kamacite, or other minerals near kamacite. By analyzing the focused ion beam ultrathin slices of laser pits with a transmission electron microscope, the results show that the subsurface structures can be divided into three classes and that npFe can be easily found in Fe‐bearing minerals. These differences in impact characteristics will help determine the source material of npFe and infer the type of micrometeorite impactors. During micrometeorite bombardment, in the mare regions, the npFe are probably produced simultaneously from lunar basalt and micrometeorites with iron‐rich minerals, while the npFe in the highlands regions mainly come from micrometeorites.

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Section: Tem Analysis Of the Irradiated Samplessupporting

confidence: 89%

Impact Characteristics of Different Rocks in a Pulsed Laser Irradiation Experiment: Simulation of Micrometeorite Bombardment on the Moon

Yao

et al. 2017

JGR Planets

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“…The euhedral nature of some nanoparticles has been recognized in immature lunar soil grains (Thompson et al. ). In the multiple thermal‐shock experiments for this work, the euhedral nanoparticles that developed after the initial heating event become more rounded/spherical with each subsequent thermal episode.…”

Section: Discussionmentioning

confidence: 99%

“…The continuum intensity has been successfully modeled with linear and step-function (arctan) fits between edge-onset and postedge energies (Garvie and Buseck 1998;van Aken et al 1998). As such, we used a linear fit between 705 and 735 eV to subtract the continuum beneath the Fe L 2,3 edge for each spectrum (Zega et al 2003;Thompson et al 2016).…”

Section: Methodsmentioning

confidence: 99%

“…Surface soils with a higher maturity, i.e., amount of exposure time to interplanetary space, have a larger concentration of npFe. Recent work has shown that these npFe can oxidize from metallic (Fe 0 ) to ferrous (Fe 2+ ) and even ferric (Fe 3+ ) Fe on the lunar surface after their formation and that oxidized Fe impacts the optical properties of the soil in which the npFe is hosted (Thompson et al 2016). An investigation of the effect that npFe size has on resulting reflectance spectra showed that small (<10 nm) nanoparticles are responsible for reddening the reflectance spectra of soils, whereas larger (>50 nm) particles cause darkening of the overall spectrum (Keller et al 1998;Noble et al 2007).…”

Section: Introductionmentioning

confidence: 99%

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In situ experimental formation and growth of Fe nanoparticles and vesicles in lunar soil

Thompson

Zega

2016

Meteorit & Planetary Scien

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We report the results of the first dynamic, in situ heating of lunar soils to simulate micrometeorite impacts on the lunar surface. We performed slow‐ and rapid‐heating experiments inside the transmission electron microscope to understand the chemical and microstructural changes in surface soils resulting from space‐weathering processes. Our slow‐heating experiments show that the formation of Fe nanoparticles begins at ~575 °C. These nanoparticles also form as a result of rapid‐heating experiments, and electron energy‐loss spectroscopy measurements indicate the Fe nanoparticles are composed entirely of Fe0, suggesting this simulation accurately mimics micrometeorite space‐weathering processes occurring on airless body surfaces. In addition to Fe nanoparticles, rapid‐heating experiments also formed vesiculated textures in the samples. Several grains were subjected to repeated thermal shocks, and the measured size distribution and number of Fe nanoparticles evolved with each subsequent heating event. These results provide insight into the formation and growth mechanisms for Fe nanoparticles in space‐weathered soils and could provide a new methodology for relative age dating of individual soil grains from within a sample population.

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“…; Thompson et al. ). In this study, the agglutinates contain pyroxene grains with large variations in texture and mineral compositions and other minerals such as plagioclase, olivine, and a silica phase.…”

Section: Discussionmentioning

confidence: 97%

Possible records of space weathering on Vesta: Case study in a brecciated eucrite Northwest Africa 1109

Wang

Zhang

Pang

et al. 2019

Meteorit & Planetary Scien

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Records of space weathering are important for understanding the formation and evolution of surface regolith on airless celestial bodies. Current understanding of space weathering processes on asteroids including asteroid‐4 Vesta, the source of the howardite–eucrite–diogenite (HED) meteorites, lags behind what is known for the Moon. In this study, we studied agglutinates, a vesicular glass‐coating lithic clast, and a fine‐grained sulfide replacement texture in the polymict breccia Northwest Africa (NWA) 1109 with electron microscopy. In agglutinates, nanophase grains of FeNi and FeS were observed, whereas npFe0 was absent. We suggested that the agglutinates in NWA 1109 formed from fine‐grained surface materials of Vesta during meteorite/micrometeorite bombardment. The fine‐grained sulfide replacement texture (troilite + hedenbergite + silica) should be a result of reaction between S‐rich vapors and pyroxferroite. The unique Fe/Mn values of relict pyroxferroite indicate a different source from normal HED pyroxenes, arguing that the reaction took place on or near the surface of Vesta. The fine‐grained sulfide replacement texture could be a product of nontypical space weathering on airless celestial bodies. We should pay attention to this texture in future returned samples by asteroid exploration missions.

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The oxidation state of nanophase Fe particles in lunar soil: Implications for space weathering

Cited by 65 publications

References 43 publications

Impact Characteristics of Different Rocks in a Pulsed Laser Irradiation Experiment: Simulation of Micrometeorite Bombardment on the Moon

Impact Characteristics of Different Rocks in a Pulsed Laser Irradiation Experiment: Simulation of Micrometeorite Bombardment on the Moon

In situ experimental formation and growth of Fe nanoparticles and vesicles in lunar soil

Possible records of space weathering on Vesta: Case study in a brecciated eucrite Northwest Africa 1109

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