Argon diffusion in Apollo 16 impact glass spherules: Implications for 40Ar/39Ar dating of lunar impact events

Determining the impact chronology of the Moon is an important yet challenging problem in planetary science even after decades of lunar samples and other analyses. In addition to crater counting statistics, orbital data, and dynamical models, well-constrained lunar sample ages are critical for proper interpretation of the Moon’s impact chronology. To understand which properties of lunar impact glasses yield well-constrained ages, we evaluated the compositions and sizes of 119 Apollo 14, 15, 16, and 17 impact glass samples whose compositions and 40Ar/39Ar ages have already been published, and we present new data on 43 others. These additional data support previous findings that the composition and size of the glass are good indicators of the quality of the age plateau derived for each sample. We have further constrained those findings: Glasses of ≥200 μm with a fraction of non-bridging oxygens (X(NBO)) of ≥0.23 and a K2O (wt%) of ≥0.07 are prime candidates for argon analyses and more likely to yield well-constrained 40Ar/39Ar ages. As a result, science resulting from impact glass analyses is maximized while analytical costs per glass are minimized. This has direct implications for future analyses of glass samples for both those in the current lunar collection and those that have yet to be collected.

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Refining lunar impact chronology through high spatial resolution 40Ar/39Ar dating of impact melts

Science Advances ◽

10.1126/sciadv.1400050 ◽

2015 ◽

Vol 1 (1) ◽

pp. e1400050 ◽

Cited By ~ 11

Author(s):

Cameron M. Mercer ◽

Kelsey E. Young ◽

John R. Weirich ◽

Kip V. Hodges ◽

Bradley L. Jolliff ◽

...

Keyword(s):

Isotope Geochronology ◽

Impact Melt ◽

Laser Microprobe ◽

Lunar Impact ◽

Multiple Impact ◽

Impact Melts ◽

Multiple Samples ◽

Impact Events ◽

Ar Geochronology ◽

Microprobe Technique

Quantitative constraints on the ages of melt-forming impact events on the Moon are based primarily on isotope geochronology of returned samples. However, interpreting the results of such studies can often be difficult because the provenance region of any sample returned from the lunar surface may have experienced multiple impact events over the course of billions of years of bombardment. We illustrate this problem with new laser microprobe 40Ar/39Ar data for two Apollo 17 impact melt breccias. Whereas one sample yields a straightforward result, indicating a single melt-forming event at ca. 3.83 Ga, data from the other sample document multiple impact melt–forming events between ca. 3.81 Ga and at least as young as ca. 3.27 Ga. Notably, published zircon U/Pb data indicate the existence of even older melt products in the same sample. The revelation of multiple impact events through 40Ar/39Ar geochronology is likely not to have been possible using standard incremental heating methods alone, demonstrating the complementarity of the laser microprobe technique. Evidence for 3.83 Ga to 3.81 Ga melt components in these samples reinforces emerging interpretations that Apollo 17 impact breccia samples include a significant component of ejecta from the Imbrium basin impact. Collectively, our results underscore the need to quantitatively resolve the ages of different melt generations from multiple samples to improve our current understanding of the lunar impact record, and to establish the absolute ages of important impact structures encountered during future exploration missions in the inner Solar System.

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Lunar Impact Events, Luminous Efficiency, and Energy of

Encyclopedia of Lunar Science ◽

10.1007/978-3-319-05546-6_116-1 ◽

2018 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

José M. Madiedo ◽

José L. Ortiz

Keyword(s):

Luminous Efficiency ◽

Lunar Impact ◽

Impact Events

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Unique properties of lunar impact glass: Nanophase metallic Fe synthesis

American Mineralogist ◽

10.2138/am.2007.2333 ◽

2007 ◽

Vol 92 (8-9) ◽

pp. 1420-1427 ◽

Cited By ~ 25

Author(s):

Y. Liu ◽

L. A. Taylor ◽

J. R. Thompson ◽

D. W. Schnare ◽

J.-S. Park

Keyword(s):

Lunar Impact ◽

Impact Glass

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NO CHANGE IN THE LUNAR IMPACT FLUX THROUGH THE COPERNICAN PERIOD FROM MODELING IMPACT GLASS SPHERULE AGE DISTRIBUTION IN LUNAR REGOLITH

10.1130/abs/2017am-306683 ◽

2017 ◽

Author(s):

Ya-Huei Huang ◽

◽

David A. Minton ◽

Nicolle E.B. Zellner ◽

Masatoshi Hirabayashi ◽

...

Keyword(s):

Lunar Regolith ◽

Age Distribution ◽

Impact Flux ◽

Lunar Impact ◽

Impact Glass

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NELIOTA: ESA's new NEO lunar impact monitoring project with the 1.2m telescope at the National Observatory of Athens

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315006973 ◽

2015 ◽

Vol 10 (S318) ◽

pp. 327-329 ◽

Cited By ~ 1

Author(s):

A. Z. Bonanos ◽

M. Xilouris ◽

P. Boumis ◽

I. Bellas-Velidis ◽

A. Maroussis ◽

...

Keyword(s):

Scientific Community ◽

The Moon ◽

National Observatory ◽

Small Aperture ◽

Web Based ◽

Impact Monitoring ◽

Lunar Impact ◽

The Impact ◽

Impact Events ◽

Near Earth Objects

AbstractNELIOTA is a new ESA activity launched at the National Observatory of Athens in February 2015 aiming to determine the distribution and frequency of small near-earth objects (NEOs) via lunar monitoring. The project involves upgrading the 1.2m Kryoneri telescope of the National Observatory of Athens, building a two fast-frame camera instrument, and developing a software system, which will control the telescope and the cameras, process the images and automatically detect NEO impacts. NELIOTA will provide a web-based user interface, where the impact events will be reported and made available to the scientific community and the general public. The objective of this 3.5 year activity is to design, develop and implement a highly automated lunar monitoring system, which will conduct an observing campaign for 2 years in search of NEO impact flashes on the Moon. The impact events will be verified, characterised and reported. The 1.2m telescope will be capable of detecting flashes much fainter than current, small-aperture, lunar monitoring telescopes. NELIOTA is therefore expected to characterise the frequency and distribution of NEOs weighing as little as a few grams.

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