“…Correlation between antiquity and ( 40 Ar/ 36 Ar) trapped (as depicted by Joy et al. ). It includes three model curves by McKay et al.…”
Section: Resultsmentioning
confidence: 91%
“…; Joy et al. []). These studies presented a model in which orphan Ar was considered as a mixture of solar wind Ar and radiogenic 40 Ar degassing from the lunar interior being reimplanted by solar wind ions into lunar surface rocks.…”
Dhofar 280 recorded a complex history on the Moon revealed by high‐resolution 40Ar‐39Ar dating. Thermal resetting occurred less than 1 Ga ago, and the rock was exposed to several impact events before and afterwards. The cosmic ray exposure (CRE) age spectrum indicates a 400 ± 40 Ma CRE on the lunar surface. A unique feature of this lunar sample is a partial loss of cosmogenic 38Ar, resulting in a (low‐temperature) CRE age plateau of about 1 Ma. This was likely caused by the same recent impact event that reset the (low‐temperature) 40Ar‐39Ar age spectrum and preceded the short transit phase to Earth of ≤1 Ma. Dhofar 280 may be derived from KREEP‐rich lunar frontside terrains, possibly associated with the Copernicus crater or with a recent impact event on the deposits of the South Pole–Aitken basin. Although Dhofar 280 is paired with Dhofar 081, their irradiation and thermal histories on the Moon were different. An important trapped Ar component in Dhofar 280 is “orphan” Ar with a low 40Ar/36Ar ratio. It is apparently a mixture of two components, one endmember with 40Ar/36Ar = 17.5 ± 0.2 and a second less well‐constrained endmember with 40Ar/36Ar ≤10. The presence of two endmembers of trapped Ar, their compositions, and the breccia ages seem to be incompatible with a previously suggested correlation between age or antiquity and the (40Ar/36Ar)trapped ratio (Eugster et al. 2001; Joy et al. 2011a). Alternatively, “orphan” Ar of this impact melt breccia may have an impact origin.
“…Correlation between antiquity and ( 40 Ar/ 36 Ar) trapped (as depicted by Joy et al. ). It includes three model curves by McKay et al.…”
Section: Resultsmentioning
confidence: 91%
“…; Joy et al. []). These studies presented a model in which orphan Ar was considered as a mixture of solar wind Ar and radiogenic 40 Ar degassing from the lunar interior being reimplanted by solar wind ions into lunar surface rocks.…”
Dhofar 280 recorded a complex history on the Moon revealed by high‐resolution 40Ar‐39Ar dating. Thermal resetting occurred less than 1 Ga ago, and the rock was exposed to several impact events before and afterwards. The cosmic ray exposure (CRE) age spectrum indicates a 400 ± 40 Ma CRE on the lunar surface. A unique feature of this lunar sample is a partial loss of cosmogenic 38Ar, resulting in a (low‐temperature) CRE age plateau of about 1 Ma. This was likely caused by the same recent impact event that reset the (low‐temperature) 40Ar‐39Ar age spectrum and preceded the short transit phase to Earth of ≤1 Ma. Dhofar 280 may be derived from KREEP‐rich lunar frontside terrains, possibly associated with the Copernicus crater or with a recent impact event on the deposits of the South Pole–Aitken basin. Although Dhofar 280 is paired with Dhofar 081, their irradiation and thermal histories on the Moon were different. An important trapped Ar component in Dhofar 280 is “orphan” Ar with a low 40Ar/36Ar ratio. It is apparently a mixture of two components, one endmember with 40Ar/36Ar = 17.5 ± 0.2 and a second less well‐constrained endmember with 40Ar/36Ar ≤10. The presence of two endmembers of trapped Ar, their compositions, and the breccia ages seem to be incompatible with a previously suggested correlation between age or antiquity and the (40Ar/36Ar)trapped ratio (Eugster et al. 2001; Joy et al. 2011a). Alternatively, “orphan” Ar of this impact melt breccia may have an impact origin.
“…Younger regoliths formed \3.5 Ga provide a window to understanding the sources of Earth-Moon-crossing impactor populations during a window of declining bombardment rates (Joy et al 2011a(Joy et al , b, 2012Fagan et al 2014). These younger samples potentially provide an archive of the types of Near Earth Objects that played a role in episodic mass extinction events here on Earth (Fagan et al 2014(Fagan et al , 2015(Fagan et al , 2016 and help to better understand the causes of such spikes (for example, the breakup of an asteroid like the L-chondrite parent body at 500 Ma: Haack et al 1996).…”
Section: Constraining Timing Of Deliverymentioning
confidence: 99%
“…3d, e). In effect, they are time capsules (McKay et al 1986(McKay et al , 1989Korotev 1996;Spudis and Taylor 2009;Crawford et al 2007Crawford et al , 2009Joy et al 2011aJoy et al , b, 2012Fagan et al 2014): once they have been turned from a soil into a coherent rock they are closed to solar wind exposure and can no longer acquire a meteoritic component. The timing of this closure event (i.e.…”
Section: Regolith Brecciasmentioning
confidence: 99%
“…Acknowledgments Material in this review article has been brought together from work published previously by , Crawford et al (2007), Joy et al (2011aJoy et al ( , b, 2012, Joy (2014), and Fagan et al (2014). We thank two anonymous reviewers for their helpful suggestions to improve the manuscript, and Dr. Gudipati for editorial handling.…”
The Moon is an archive of impact cratering in the Solar System throughout the past 4.5 billion years. It preserves this record better than larger, more complex planets like the Earth, Mars and Venus, which have largely lost their ancient crusts through geological reprocessing and hydrospheric/atmospheric weathering. Identifying the parent bodies of impactors (i.e. asteroid bodies, comets from the Kuiper belt or the Oort Cloud) provides geochemical and chronological constraints for models of Solar System dynamics, helping to better inform our wider understanding of the evolution of the Solar System and the transfer of small bodies between planets. In this review article, we discuss the evidence for populations of impactors delivered to the Moon at different times in the past. We also propose approaches to the identification and characterisation of meteoritic material on the Moon in the context of future lunar exploration efforts.
Future sustained human presence on the Moon will require us to make use of lunar resources. This in‐situ resource utilisation (ISRU) process will require suitable feedstock (i.e., lunar regolith) that has been both acquired and prepared (or beneficiated) to set standards. Acquisition of pre‐processed regolith, is an often overlooked engineering challenge in the demanding and low‐gravity environment of the lunar surface. Currently, regolith excavation and size separation are often developed independently of each other. Here, we present the Lunar Excavation and Size Separation System (LES3), which is an engineered one‐system solution to combine the acquisition of lunar regolith as well as separate it into two distinct size fractions, and therefore, can assist to define the quality of the feedstock material for ISRU processes. Intended for use with a lightweight (40–60 kg) lunar rover (LUnar Volatiles Mobile Instrumentation‐X; LUVMI‐X) currently under development, the mechanism utilises vibrations to reduce excavation forces and facilitate size separation. Low excavation forces are crucial for lunar excavators to be deployable on lightweight robotic platforms as limited traction forces are available. The rationale behind the mechanism is explained, its capabilities in the support of science and ISRU are showcased, and results from several laboratory test campaigns, including tests of gravitational dry sieving of different regolith simulants, are presented. The LES3 can excavate up to 100 g in a single charge while maintaining excavation forces of less than 8 N and having a mass of less than 2 kg. Finally, areas of improvement for a second iteration of the design are presented and explained. The LES3 proof of concept shows that combining of regolith excavation and size‐separation in a single mechanism is feasible.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
