The timeline of the lunar bombardment: Revisited

Morbidelli, Alessandro; Nesvorný, David; Laurenz, Vera; Marchi, S.; Rubie, D. C.; Elkins-Tanton, Linda T.; Wieczorek, M. A.; Jacobson, Seth A.

doi:10.1016/j.icarus.2017.12.046

Cited by 229 publications

(291 citation statements)

References 131 publications

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“…Accordingly, the basins classified within stratigraphic age groups 1–4, which account for ~40% of the total number of basins and 32% of the “definite” basins chronologically ordered by Wilhelms (), would have likely formed prior to ~4.3 Ga. It should be noted that the implications of this constraint for the crater chronology of the Moon, and the existence and timing of a late heavy bombardment in particular (e.g., Kamata et al, ; Morbidelli et al, , ), depend heavily on the poorly constrained absolute age for Nectaris as well as the absolute ages for the younger pre‐Nectarian basins (stratigraphic age groups 5–9) that are not considered herein due to their small sizes ( D < 650 km).…”

Section: Results: Relative Ages Of Lunar Terranes and Major Impact Bamentioning

confidence: 99%

Reexamination of Early Lunar Chronology With GRAIL Data: Terranes, Basins, and Impact Fluxes

et al. 2018

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Flooding of the lunar surface by ancient mare basalts has rendered uncertain the ages of lunar geochemical terranes and several impact basins. Here we combine craters having recognizable surface expressions with craters identified only by their gravitational signatures in Gravity Recovery and Interior Laboratory data to reassess the chronological sequence of lunar impact basins and the ages of major lunar geochemical terranes. Our results indicate that although volcanically flooded regions are deficient in craters with diameters greater than 20 km by more than 50% relative to unflooded regions, craters with diameters greater than 90 km can be readily recognized either by topography or by gravity anomaly. On the basis of the areal density of craters with diameters greater than 90 km we conclude that (1) the Serenitatis basin could be as young as the Imbrium basin; (2) the areal density of craters within the Procellarum KREEP Terrane is significantly lower than that for the South Pole‐Aitken basin and the Feldspathic Highlands Terrane; (3) if the youngest age of final crystallization of the lunar magma ocean is adopted as a lower bound on the age of the Procellarum KREEP Terrane, a minimum age of approximately 4.3 Ga is inferred for ~40% of lunar impact basins, including South Pole‐Aitken; and (4) the flux of impactors capable of forming craters with diameters of at least 90 km decreased substantially through the Nectarian and Imbrian periods.

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Section: Results: Relative Ages Of Lunar Terranes and Major Impact Bamentioning

confidence: 99%

Reexamination of Early Lunar Chronology With GRAIL Data: Terranes, Basins, and Impact Fluxes

et al. 2018

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“…Thus, in the spirit of "when you have eliminated the impossible, whatever remains, however improbable, must be the truth" (Doyle 1890), we identify the leftovers of the terrestrial planet accretion to be the chief suspect. The recent work of Morbidelli et al (2016) models the leftover contribution in detail and shows that it can match many constraints, including the Mars-to-Moon ratio discussed in Section 5.…”

Section: Discussionmentioning

confidence: 95%

Modeling the Historical Flux of Planetary Impactors

Nesvorný¹,

Roig²,

Bottke³

2017

117

221

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The impact cratering record of the Moon and the terrestrial planets provides important clues about the formation and evolution of the Solar System. Especially intriguing is the epoch ≃3.8-3.9 Gyr ago (Ga), known as the Late Heavy Bombardment (LHB), when the youngest lunar basins such as Imbrium and Orientale formed. The LHB was suggested to originate from a slowly declining impactor flux or from a late dynamical instability. Here we develop a model for the historical flux of large asteroid impacts and discuss how it depends on various parameters, including the time and nature of the planetary migration/instability. We find that the asteroid impact flux dropped by 1 to 2 orders of magnitude during the first 1 Gyr and remained relatively unchanged over the last 3 Gyr. The early impacts were produced by asteroids whose orbits became excited during the planetary migration/instability, and by those originating from the inner extension of the main belt (E-belt; semimajor axis 1.6 < a < 2.1 au). The inner main belt dominated the asteroid impact record after ∼3-4 Ga. The profiles obtained for the early and late versions of the planetary instability initially differ, but end up being similar after ∼3 Ga. Thus, the time of the instability can only be determined by considering the cratering and other constraints during the first ≃1.5 Gyr of the Solar System history. Our absolute calibration of the impact flux indicates that asteroids were probably not responsible for the LHB, independently of whether the instability happened early or late, because the calibrated flux is not large enough to explain Imbrium/Orientale and a significant share of large lunar craters. Comets and leftovers of the terrestrial planet formation provided additional, and probably dominant source of impacts during early epochs. The cometary impacts occur during a narrow interval after the instability and would not be recorded on surfaces if the planetary instability happened early.-2 -

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“…Without a clearer understanding of the Moon's impact history, and a resolution to the long‐standing debate surrounding the potential ~3900 Ma lunar cataclysm (Bottke and Norman and references therein; Morbidelli et al. and references therein), it is difficult to say which of the first two interpretations are more likely.…”

Section: Discussionmentioning

confidence: 99%

“…As discussed earlier, considering the susceptibility of the apatite U-Pb system to be reset by impact events, and the observed tendency for phosphate phases analyzed in Apollo breccias to be completely reset (e.g., Nemchin et al 2009b;Snape et al 2016;Thiessen et al 2017Thiessen et al , 2018, the third interpretation seems slightly less likely. Without a clearer understanding of the Moon's impact history, and a resolution to the long-standing debate surrounding the potential~3900 Ma lunar cataclysm (Bottke and Norman [2017] and references therein; Morbidelli et al [2018] and references therein), it is difficult to say which of the first two interpretations are more likely.…”

Section: Implications For the Age Resetting History Of Mil 13317mentioning

confidence: 99%

The early geological history of the Moon inferred from ancient lunar meteorite Miller Range 13317

Curran

Joy

Snape

et al. 2019

Meteorit & Planetary Scien

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Miller Range (MIL) 13317 is a heterogeneous basalt‐bearing lunar regolith breccia that provides insights into the early magmatic history of the Moon. MIL 13317 is formed from a mixture of material with clasts having an affinity to Apollo ferroan anorthosites and basaltic volcanic rocks. Noble gas data indicate that MIL 13317 was consolidated into a breccia between 2610 ± 780 Ma and 1570 ± 470 Ma where it experienced a complex near‐surface irradiation history for ~835 ± 84 Myr, at an average depth of ~30 cm. The fusion crust has an intermediate composition (Al2O3 15.9 wt%; FeO 12.3 wt%) with an added incompatible trace element (Th 5.4 ppm) chemical component. Taking the fusion crust to be indicative of the bulk sample composition, this implies that MIL 13317 originated from a regolith that is associated with a mare‐highland boundary that is KREEP‐rich (i.e., K, rare earth elements, and P). A comparison of bulk chemical data from MIL 13317 with remote sensing data from the Lunar Prospector orbiter suggests that MIL 13317 likely originated from the northwest region of Oceanus Procellarum, east of Mare Nubium, or at the eastern edge of Mare Frigoris. All these potential source areas are on the near side of the Moon, indicating a close association with the Procellarum KREEP Terrane. Basalt clasts in MIL 13317 are from a very low‐Ti to low‐Ti (between 0.14 and 0.32 wt%) source region. The similar mineral fractionation trends of the different basalt clasts in the sample suggest they are comagmatic in origin. Zircon‐bearing phases and Ca‐phosphate grains in basalt clasts and matrix grains yield 207Pb/206Pb ages between 4344 ± 4 and 4333 ± 5 Ma. These ancient 207Pb/206Pb ages indicate that the meteorite has sampled a range of Pre‐Nectarian volcanic rocks that are poorly represented in the Apollo, Luna, and lunar meteorite collections. As such, MIL 13317 adds to the growing evidence that basaltic volcanic activity on the Moon started as early as ~4340 Ma, before the main period of lunar mare basalt volcanism at ~3850 Ma.

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The timeline of the lunar bombardment: Revisited

Cited by 229 publications

References 131 publications

Reexamination of Early Lunar Chronology With GRAIL Data: Terranes, Basins, and Impact Fluxes

Reexamination of Early Lunar Chronology With GRAIL Data: Terranes, Basins, and Impact Fluxes

Modeling the Historical Flux of Planetary Impactors

The early geological history of the Moon inferred from ancient lunar meteorite Miller Range 13317

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