Complexities in pyroxene compositions derived from absorption band centers: Examples from Apollo samples, <scp>HED</scp> meteorites, synthetic pure pyroxenes, and remote sensing data

Moriarty, D. P.; Pieters, C. M.

doi:10.1111/maps.12588

Cited by 35 publications

(67 citation statements)

References 52 publications

(192 reference statements)

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“…Therefore, the spectral properties of one pyroxene with a particular mineralogy will not be equivalent to the spectral properties of a material containing a variety of pyroxenes with the same average mineralogy as that one pyroxene. Moriarty and Pieters () have previously noted that the relationship between band centers and mineralogy for synthetic pyroxenes is different than the relationship between band centers and mineralogy for naturally occurring pyroxenes. We argue that formulas for deriving asteroid pyroxene mineralogies should be derived from meteoritic spectra with measured compositions since this material will best reflect the compositions of asteroids, which are physical mixtures of a variety of different pyroxenes.…”

Section: Resultsmentioning

confidence: 97%

Can Formulas Derived From Pyroxenes and/or HEDs Be Used to Determine the Mineralogies of V‐Type Asteroids?

et al. 2018

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We compare methods for determining the pyroxene mineralogies of V‐type near‐Earth asteroids from their reflectance spectra. We evaluate whether band centers derived from the spectra of synthetic pyroxenes can be used to achieve greater analytical accuracy than is achieved through the use of band centers derived from the spectra of basaltic achondrites (howardites, eucrites, diogenites or HEDs). We conclude that band centers derived from the reflectance spectra of synthetic pyroxenes with known mineralogies do not provide useful diagnostic information to derive equations for determining accurate pyroxene compositions of V‐type asteroids. Band centers from the reflectance spectra of HEDs with known pyroxene mineralogies can be used to derive equations for determining accurate pyroxene compositions of V‐type asteroids. HEDs are physical mixtures of a number of different types of pyroxenes and best simulate the surfaces of V‐type asteroids. Formulas using the Band I center appear best for determining asteroid pyroxene mineralogies for V‐type asteroids due to the current difficulty in doing accurate temperature corrections to the Band II center. Most of the observed V‐type near‐Earth asteroids have interpreted mineralogies similar to eucrites or howardites. One of the observed near‐Earth asteroids could possibly have a surface mineralogy similar to diogenites.

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Section: Resultsmentioning

confidence: 97%

Can Formulas Derived From Pyroxenes and/or HEDs Be Used to Determine the Mineralogies of V‐Type Asteroids?

et al. 2018

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“…It is important to note that each individual sample from the LRMCC and LSCC collections contain a range of pyroxene components resulting from several natural factors such as cooling history, mineral exsolution, and physical mixing (for breccias and soils). As emphasized by Moriarty and Pieters (), band center values from remote sensing data represent composite absorption bands resulting from highly complex, nonlinear mixtures of many pyroxene and nonpyroxene components. While the relationship between pure pyroxene compositions and band centers is well established by crystal physics (Burns, ; Klima et al, ; Klima, Dyar, & Pieters, ), natural materials are inevitably mixtures whether they be a pristine rock, well‐developed soil, or surface swaths measured via remote sensing.…”

Section: Discussion and Integrationmentioning

confidence: 99%

“…All optical subperiods used here (except OP2C2) correspond to a single temperature state of the detector Figure 2. Example derivation of spectral parameters using an approach involving Parabolic band fits after a two-part Linear Continuum removal (PLC, discussed further in the text, supporting information, and Moriarty & Pieters, 2016a). (a) Laboratory reflectance spectra (solid) with estimated two-part linear continua (dashed) for two pure pyroxenes (orthopyroxene En35,Fs65, RELAB #DL-CMP-025; clinopyroxene En39, Fs34, Wo27, RELAB #DL-CMP-051, discussed further in Klima et al, 2007, and.…”

Section: Plc Analyses Of Pyroxene Composition and Abundancementioning

confidence: 99%

The Character of South Pole‐Aitken Basin: Patterns of Surface and Subsurface Composition

2018

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Using Moon Mineralogy Mapper data, we characterize surface diversity across the enormous South Pole‐Aitken Basin (SPA) by evaluating the abundance and composition of pyroxenes, which are overwhelmingly the most abundant mafic mineral in the region. Although SPA exhibits significant complexity due to billions of years of geologic processes subsequent to formation, the basin has retained regular patterns of compositional heterogeneity across its structure. Four distinct, roughly concentric zones are defined: (1) a central SPA compositional anomaly, which exhibits a pervasive elevated Ca,Fe‐rich pyroxene abundance; (2) a Mg‐pyroxene annulus, which is dominated by abundant Mg‐rich pyroxenes; (3) a heterogeneous annulus, which exhibits localized pyroxene‐rich areas spatially mixed with feldspathic materials; and (4) the SPA exterior, which is primarily feldspathic. Pyroxene compositions in the heterogeneous annulus are similar to those in the Mg‐pyroxene annulus, and Mg‐rich pyroxenes also underlie the more Ca,Fe‐rich pyroxene surface material across the SPA compositional anomaly. The establishment of these four distinct compositional zones across SPA constrains basin evolution models and serves to guide potential sample return (and other science) targets.

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“…(a) Parameter map of the 1‐μm band depth, derived from M 3 image M3G20090604T191631 using the Parabolas and two‐part Linear Continua (PLC) technique developed and validated by Moriarty and Pieters (). This parameter is sensitive primarily to the abundance of mafic minerals (which on the lunar surface is predominantly pyroxene).…”

Section: Methodsmentioning

confidence: 99%

“…From the Diviner PDSarchived Reduced Data Record data set, we selected rectangular regions of interest containing at least 100 radiogenic measurements taken with emission angles less than 2°off nadir and local solar times between 9:00 and 15:00. Using the method of Greenhagen et al (2010Greenhagen et al ( , 2011, we normalized the data to equatorial noon, fit the Diviner Channels 3, 4, and 5 (7.8, 8.28, and 8.55 μm) using a second-order polynomial, and Moriarty and Pieters (2016). This parameter is sensitive primarily to the abundance of mafic minerals (which on the lunar surface is predominantly pyroxene).…”

Section: Christiansen Feature Analysismentioning

confidence: 99%

Impact Melt Facies in the Moon's Crisium Basin: Identifying, Characterizing, and Future Radiogenic Dating

et al. 2020

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Both Earth and the Moon share a common history regarding the epoch of large basin formation, though only the lunar geologic record preserves any appreciable record of this Late Heavy Bombardment. The emergence of Earth's first life is approximately contemporaneous with the Late Heavy Bombardment; understanding the latter informs the environmental conditions of the former, which are likely necessary to constrain the mechanisms of abiogenesis. While the relative formation time of most of the Moon's large basins is known, the absolute timing is not. The timing of Crisium Basin's formation is one of many important events that must be constrained and would require identifying and dating impact melt formed in the Crisium event. To inform a future lunar sample dating mission, we thus characterized possible outcrops of impact melt. We determined that several mare lava-embayed kipukas could contain impact melt, though the rim and central peaks of the partially lava-flooded Yerkes Crater likely contain the most pure and intact Crisium impact melt. It is here where future robotic and/or human missions could confidently add a key missing piece to the puzzle of the combined issues of early Earth-Moon bombardment and the emergence of life.Plain Language Summary How could life get started on Earth nearly four billion years ago if our planet was constantly being impacted by asteroids and comets? While we do not yet know, we are starting to piece together parts of the answer. Earth's largest impact basins are long gone because of our planet's active geology, life, and flowing water. But the Moon's big craters are well preserved. The formation of those large basins melted lots of rocks, which then cooled; by collecting those rocks on future missions and figuring out how old they are, we can determine the timing of when large basins formed on the Moon and, by extension, on Earth. Crisium basin is one of those large basins that we need to get the age for. Most of the rock that was melted from this impact and then cooled is buried by much younger lava flows, but we believe that some of it was brought up when the crater Yerkes formed on top of Crisium. The central mountain of Yerkes Crater is where we believe future robots and/or astronauts should go to collect once-molten rock and figure out how old it and the basin are.

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Complexities in pyroxene compositions derived from absorption band centers: Examples from Apollo samples, HED meteorites, synthetic pure pyroxenes, and remote sensing data

Cited by 35 publications

References 52 publications

Can Formulas Derived From Pyroxenes and/or HEDs Be Used to Determine the Mineralogies of V‐Type Asteroids?

Can Formulas Derived From Pyroxenes and/or HEDs Be Used to Determine the Mineralogies of V‐Type Asteroids?

The Character of South Pole‐Aitken Basin: Patterns of Surface and Subsurface Composition

Impact Melt Facies in the Moon's Crisium Basin: Identifying, Characterizing, and Future Radiogenic Dating

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