Reflectance spectroscopy of chromium-bearing spinel with application to recent orbital data from the Moon

Williams, K. B.; Jackson, Colin R.; Cheek, L. C.; Donaldson-Hanna, K.; Parman, S. W.; Pieters, C. M.; Dyar, M. D.; Prissel, T. C.

doi:10.2138/am-2016-5535

Cited by 18 publications

(21 citation statements)

References 32 publications

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“…Additionally, space weathering causes the overall reflectance and strength of absorptions to decrease, hindering our ability to identify features associated with specific spinel compositions. With these limitations to the interpretation of M 3 spectra in mind, it seems that our spectra best support the experimental and laboratory results by Williams et al () that favor an Al‐ and Fe‐rich pleonaste spinel for the SA spinels relative to the more common PSAs.…”

Section: Discussionsupporting

confidence: 85%

“…Nevertheless, the SA spinel-rich areas are associated with very dark mantling materials with low albedos whereas the PSAs are all associated with feldspathic regions and exhibit no albedo distinctions from their surroundings in the visible. Williams et al (2016) found that increasing the content of octahedral Fe 2+ increases the strength of the absorption band near 700 nm, which may explain many of our spectra that exhibit an absorption around this wavelength. However, experiments by Jackson et al (2014) show that increasing Fe content in the aluminate spinels should produce both a weaker 700 nm and a stronger 1000 nm band (see Figure 2 in Jackson et al, 2014), which we only observed in spectra taken from Gambart B and G craters ( Figure 14).…”

Section: Discussionmentioning

confidence: 71%

“…Williams et al () found that increasing the content of octahedral Fe 2+ increases the strength of the absorption band near 700 nm, which may explain many of our spectra that exhibit an absorption around this wavelength. However, experiments by Jackson et al () show that increasing Fe content in the aluminate spinels should produce both a weaker 700 nm and a stronger 1000 nm band (see Figure 2 in Jackson et al, ), which we only observed in spectra taken from Gambart B and G craters (Figure ).…”

Section: Discussionmentioning

confidence: 75%

“…However, none of the spinel spectra show an absorption at 1250 nm that is attributed to Cr 2+ in terrestrial Cr‐spinels (Cloutis et al, ). Experimental work performed to mimic lunar conditions by Jackson et al () and Williams et al () indicates that the 1250 nm absorption would not be expected for lunar Cr‐spinels because the chromium is present as octahedral Cr 3+ . Instead, a narrow band near 550 nm would indicate octahedral Cr 3+ and bands near 1000, 2000, and 2800 nm are associated with Fe.…”

Section: Discussionmentioning

confidence: 99%

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Investigation of Lunar Spinels at Sinus Aestuum

et al. 2017

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Sinus Aestuum is the only known location on the Moon where orbital data have detected Fe‐and/or Cr‐spinel. We analyzed Moon Mineralogy Mapper (M3) visible to near‐infrared data of the largest and strongest spinel signatures and determined that these locations always correspond to impact craters. M3 spectra show that at least three types of spinels may be present, all of which exhibit a strong and broad absorption at ~2100 nm, and also one of the following: (1) a narrow 700–750 nm absorption, (2) a broad 600–900 nm absorption, or (3) both a weaker 700 nm and stronger 1000 nm absorption. All the spinel detections occur on either larger highland massifs that make up Sinus Aestuum east and west or smaller highland kīpukas and buried highlands within the mare. Almost all of the spinel signatures occur within the mapped pyroclastic dark mantle deposit (DMD). The strong correlation between spinel and DMD distribution on the highlands at Sinus Aestuum is best explained if the spinels were emplaced during the same explosive eruption(s) that deposited the pyroclastics in the Sinus Aestuum DMD. Our observations are most consistent with models of melt‐rock reactions in the anorthositic lunar crust that produce contaminated (high‐Al) regions within a volcanic dike or magmatic reservoir that was capable of erupting pyroclastic glass beads containing pleonaste spinel [Mg,Fe]Al2O4. Over billions of years, this surface layer of spinels and pyroclastics became heterogeneously mixed into and partially buried within the highland regolith where younger impact craters may sometimes expose it.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 71%

Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

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Investigation of Lunar Spinels at Sinus Aestuum

et al. 2017

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“…The pyroxenes are broadly quadrilateral in composition and abundant in lunar basalts (e.g., Papike et al, 1976;Papike & Vaniman, 1978), and olivine is generally Fo 30-80 (e.g., Wieczorek et al, 2006). Additionally, the oxide ilmenite is abundant in some mare basalts (McKay & Williams, 1979;Rutherford et al, 1980) and spinel has been shown to be an important phase based on both laboratory and remote sensing studies Marriner et al, 2014Marriner et al, , 2015Nekvasil et al, 2015;Pieters et al, 2011Pieters et al, , 2014Williams et al, 2016). Analyses of sieved bulk Apollo soils have shown an average particle size of~60 μm, with a median range between 40 and 130 μm with a depth dependence where material at the top of the regolith column has a smaller average particle size (Carrier, 1973;Heiken et al, 1973;King et al, 1971King et al, , 1972aKing et al, , 1972bMcKay et al, 1972McKay et al, , 1974.…”

Section: The Lunar Regolithmentioning

confidence: 99%

Particle Size Effects on Mid‐Infrared Spectra of Lunar Analog Minerals in a Simulated Lunar Environment

Shirley

Glotch

2019

JGR Planets

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Mid‐infrared spectroscopic analysis of the Moon and other airless bodies requires a full accounting of spectral variation due to the unique thermal environment in airless body regoliths and the substantial differences between spectra acquired under airless body conditions and those measured in an ambient environment on Earth. Because there exists a thermal gradient within the upper hundreds of microns of lunar regolith, the data acquired by the Diviner Lunar Radiometer Experiment are not isothermal with wavelength. While this complication has been previously identified, its effect on other known variables that contribute to spectral variation, such as particle size and porosity, have yet to be well characterized in the laboratory. Here we examine the effect of particle size on mid‐infrared spectra of silicates common to the Moon measured within a simulated lunar environment chamber. Under simulated lunar conditions, decreasing particle size is shown to enhance the spectral contrast of the Reststrahlen bands and transparency features, as well as shift the location of the Christiansen feature to longer wavelengths. This study shows that these variations are detectable at Diviner spectral resolution and emphasizes the need for simulated environment laboratory data sets, as well as hyperspectral mid‐infrared instruments on future missions to airless bodies.

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