Reflectance spectra of seven lunar swirls examined by statistical methods: A space weathering study

Flanderová, Kateřina; Kohout, T.; Ďurech, Josef

doi:10.1016/j.icarus.2019.05.024

Cited by 8 publications

(6 citation statements)

References 52 publications

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“…Highly porous and fine-grained regolith often referred to as "fairy castle" (Hapke & van Horn 1963) is created by gardening of the regolith by micrometeorites and solar radiation (e.g., Hapke & van Horn 1963). This would, however, suggest that the magnetic field shields the surface also from micrometeorite impact, which is generally assumed to be not the case (e.g., Chrbolkova et al 2019), or that the high porosity of mature regolith is mainly caused by charged particles of the solar wind rather than by micrometeorites, which would be physically unintuitive.…”

Section: Discussionmentioning

confidence: 99%

“…Figure A.1e shows the mean spectrum of the region. The eigenvectors of the covariance matrix, the so-called principal components, contain information about trends in the data but are usually difficult to interpret in an intuitive way (e.g., Chrbolkova et al 2019). However, in this special case the first component, describing most of the variance in the data, can be interpreted to contain information about the 1 µm and 2 µm absorption bands (Fig.…”

Section: On-swirl Vs Off-swirl Spectral Trendsmentioning

confidence: 99%

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Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

Hess

Wöhler

Bhatt

et al. 2020

A&A

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We investigated six bright swirls associated with magnetic anomalies of variable strength using Chandrayaan-1 Moon Mineralogy Mapper (M3) hyperspectral image data. We examined the 3 μm absorption band generally ascribed to solar wind-induced OH/H2O and spectral trends in the near-infrared wavelength range at on-swirl and off-swirl locations. We found that the 3 μm absorption band is weaker at on-swirl than at off-swirl locations and shows only weak variations with time-of-day. This result is consistent with magnetic anomaly shielding that reduces solar wind interaction with the surface. For a small swirl structure in Mare Moscoviense, we found the 3 μm absorption band to be similar to that of its surroundings due to the absence of strong magnetic shielding. Our spectral analysis results at on-swirl and off-swirl locations suggest that the spectral trends at on-swirl and off-swirl locations cannot always be explained by reduced space-weathering alone. We propose that a combination of soil compaction possibly resulting from the interaction between the surface and cometary gas and subsequent magnetic shielding is able to explain all observed on-swirl vs. off-swirl spectral trends including the absorption band depth near 3 μm. Our results suggest that an external mechanism of interaction between a comet and the uppermost regolith layer might play a significant role in lunar swirl formation.

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Section: Discussionmentioning

confidence: 99%

Section: On-swirl Vs Off-swirl Spectral Trendsmentioning

confidence: 99%

Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

Hess

Wöhler

Bhatt

et al. 2020

A&A

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“…This dimensionality reduction technique takes an m-dimensional cloud of points, where m is the number of wavelengths in the spectral data, and transforms it so that in the new orthogonal coordinate space the first coordinate (first principal component, PC1) corresponds to the direction in which the original cloud showed the greatest variance, the second coordinate (PC2) represents the direction with the second greatest variance, and so on. The new coordinate system usually does not have an exact physical meaning, but its usefulness has been proven in previous research: for example, for asteroid taxonomy based on PCA, see DeMeo et al (2009); for analysis of meteorite spectra, see Penttilä et al (2018); for research on the lunar magnetic anomalies, see Chrbolková et al (2019) and Kramer et al (2011); and for PCA applied to the spectra of galaxies, see Connolly & VanderPlas (2014).…”

Section: Principal Component Analysismentioning

confidence: 99%

Comparison of space weathering spectral changes induced by solar wind and micrometeoroid impacts using ion- and femtosecond-laser-irradiated olivine and pyroxene

Flanderová

Brunetto

Ďurech

et al. 2021

A&A

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Context. Space weathering is a process that changes the surface of airless planetary bodies. Prime space weathering agents are solar wind irradiation and micrometeoroid bombardment. These processes alter planetary reflectance spectra and often modify their compositional diagnostic features. Aims. In this work we focused on simulating and comparing the spectral changes caused by solar wind irradiation and by micrometeoroid bombardment to gain a better understanding of these individual space weathering processes. Methods. We used olivine and pyroxene pellets as proxies for planetary materials. To simulate solar wind irradiation we used hydrogen, helium, and argon ions with energies from 5 to 40 keV and fluences of up to 1018 particles cm−2. To simulate micrometeoroid bombardment we used individual femtosecond laser pulses. We analysed the corresponding evolution of different spectral parameters, which we determined by applying the Modified Gaussian Model, and we also conducted principal component analysis. Results. The original mineralogy of the surface influences the spectral evolution more than the weathering agent, as seen from the diverse evolution of the spectral slope of olivine and pyroxene upon irradiation. The spectral slope changes seen in olivine are consistent with observations of A-type asteroids, while the moderate to no slope changes observed in pyroxene are consistent with asteroid (4) Vesta. We also observed some differences in the spectral effects induced by the two weathering agents. Ions simulating solar wind have a smaller influence on longer wavelengths of the spectra than laser irradiation simulating micrometeoroid impacts. This is most likely due to the different penetration depths of ions and laser pulses. Our results suggest that in some instances it might be possible to distinguish between the contributions of the two agents on a weathered surface.

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“…The high-reflectance portion of lunar swirls closely resemble immature material in some ways, with similar bulk SMFe abundances, but differ in the abundance of the smallest scale particles (<15 nm), or nsFe abundances (Trang & Lucey, 2019;Chrbolková et al, 2019;Blewett et al, 2021a). This is interpreted to be the result of decreased solar wind weathering due to charged-particle deflection by swirl-associated MAs.…”

Section: Figurementioning

confidence: 85%

Ultraviolet and magnetic perspectives at Reiner Gamma and the implications for solar wind weathering

Waller¹,

Cahill²,

Retherford

et al. 2022

Front. Astron. Space Sci.

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With the wealth of missions selected to visit the lunar surface in the decade ahead, preparatory investigations into surface conditions are underway to explore potential challenges and science returns during these missions. One such mission, Lunar Vertex, is slated to explore a much-anticipated region–the lunar swirl and magnetic anomaly known as Reiner Gamma. Lunar swirls are unique natural laboratories for exploring solar wind interactions with partially magnetized rocky bodies, and possess characteristics that have not yet been observed on any other body in the Solar System. This work aims to combine current magnetic mapping of Reiner Gamma with ultraviolet wavelength datasets, towards further understanding the sensitivities of ultraviolet measurements in regions that may be partially magnetically shielded from solar wind weathering and magnetospheric plasma populations. Observations and models herein are collected and derived from orbital sources and will be used for comparison to future orbital and surface observations of Reiner Gamma by Lunar Vertex.

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Reflectance spectra of seven lunar swirls examined by statistical methods: A space weathering study

Cited by 8 publications

References 52 publications

Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

Processes governing the VIS/NIR spectral reflectance behavior of lunar swirls

Comparison of space weathering spectral changes induced by solar wind and micrometeoroid impacts using ion- and femtosecond-laser-irradiated olivine and pyroxene

Ultraviolet and magnetic perspectives at Reiner Gamma and the implications for solar wind weathering

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