The timeline of the lunar bombardment: Revisited

A. Morbidelli, D. Nesvorny, V. Laurenz, S. Marchi, D. C. Rubie, Linda Elkins-Tanton, M. Wieczorek, S. Jacobson

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

The timeline of the lunar bombardment in the first Gy of Solar System history remains unclear. Basin-forming impacts (e.g. Imbrium, Orientale), occurred 3.9–3.7 Gy ago, i.e. 600–800 My after the formation of the Moon itself. Many other basins formed before Imbrium, but their exact ages are not precisely known. There is an intense debate between two possible interpretations of the data: in the cataclysm scenario there was a surge in the impact rate approximately at the time of Imbrium formation, while in the accretion tail scenario the lunar bombardment declined since the era of planet formation and the latest basins formed in its tail-end. Here, we revisit the work of Morbidelli et al. (2012) that examined which scenario could be compatible with both the lunar crater record in the 3–4 Gy period and the abundance of highly siderophile elements (HSE) in the lunar mantle. We use updated numerical simulations of the fluxes of asteroids, comets and planetesimals leftover from the planet-formation process. Under the traditional assumption that the HSEs track the total amount of material accreted by the Moon since its formation, we conclude that only the cataclysm scenario can explain the data. The cataclysm should have started ∼ 3.95 Gy ago. However we also consider the possibility that HSEs are sequestered from the mantle of a planet during magma ocean crystallization, due to iron sulfide exsolution (O'Neil, 1991; Rubie et al., 2016). We show that this is likely true also for the Moon, if mantle overturn is taken into account. Based on the hypothesis that the lunar magma ocean crystallized about 100–150 My after Moon formation (Elkins-Tanton et al., 2011), and therefore that HSEs accumulated in the lunar mantle only after this timespan, we show that the bombardment in the 3–4 Gy period can be explained in the accretion tail scenario. This hypothesis would also explain why the Moon appears so depleted in HSEs relative to the Earth. We also extend our analysis of the cataclysm and accretion tail scenarios to the case of Mars. The accretion tail scenario requires a global resurfacing event on Mars ∼ 4.4 Gy ago, possibly associated with the formation of the Borealis basin, and it is consistent with the HSE budget of the planet. Moreover it implies that the Noachian and pre-Noachian terrains are ∼ 200 My older than usually considered.

Original languageEnglish (US)
Pages (from-to)262-276
Number of pages15
JournalIcarus
Volume305
DOIs
StatePublished - May 1 2018

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Moon
bombardment
moon
planet
lunar mantle
accretion
siderophile element
planets
siderophile elements
basin
Mars
magma
mantle
mars
overturn
oceans
Earth mantle
planetesimal
iron sulfide
exsolution

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Morbidelli, A., Nesvorny, D., Laurenz, V., Marchi, S., Rubie, D. C., Elkins-Tanton, L., ... Jacobson, S. (2018). The timeline of the lunar bombardment: Revisited. Icarus, 305, 262-276. https://doi.org/10.1016/j.icarus.2017.12.046

The timeline of the lunar bombardment : Revisited. / Morbidelli, A.; Nesvorny, D.; Laurenz, V.; Marchi, S.; Rubie, D. C.; Elkins-Tanton, Linda; Wieczorek, M.; Jacobson, S.

In: Icarus, Vol. 305, 01.05.2018, p. 262-276.

Research output: Contribution to journalArticle

Morbidelli, A, Nesvorny, D, Laurenz, V, Marchi, S, Rubie, DC, Elkins-Tanton, L, Wieczorek, M & Jacobson, S 2018, 'The timeline of the lunar bombardment: Revisited', Icarus, vol. 305, pp. 262-276. https://doi.org/10.1016/j.icarus.2017.12.046
Morbidelli A, Nesvorny D, Laurenz V, Marchi S, Rubie DC, Elkins-Tanton L et al. The timeline of the lunar bombardment: Revisited. Icarus. 2018 May 1;305:262-276. https://doi.org/10.1016/j.icarus.2017.12.046
Morbidelli, A. ; Nesvorny, D. ; Laurenz, V. ; Marchi, S. ; Rubie, D. C. ; Elkins-Tanton, Linda ; Wieczorek, M. ; Jacobson, S. / The timeline of the lunar bombardment : Revisited. In: Icarus. 2018 ; Vol. 305. pp. 262-276.
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