Timing of Late Accretion

The overarching goal of project area A is to quantify the inner solar system’s impactor flux during late accretion, by reconstructing the cratering record of the Moon and the chronology of its crust.


The long-term goal of project area A is to quantify the inner solar system's late accretion history by disentangling the lunar bombardment record. Results of the first funding period indicate the great potential of isotopic dating by improved isochron and in situ U-Pb methods to better understand the behavior of these systems in lunar impactites (subproject A1). Coupling of different methodological approaches such as CSFD-based chronology (subprojects A2 and A3), isotopic dating, modeling of gravity combined with topography data, crater formation, and the progressive mixing of impact melt into the lunar crust as a consequence of impact gardening (subproject A4) proved to be a promising strategy to achieve project area A's long-term goal.

Major research objectives and questions

  1. Can a chronological bias between Ar-Ar and U-Pb for lunar impactites be verified with further analyses, and when did the oldest known basins on the Moon form? (subprojects A1, A5)
  2. How is the chronology and preservation of lunar crust related to the cratering record of the lunar surface? (subprojects A1, A4, A5, C4)
  3. What is the complete inventory of detectable impact basins and their sequence of formation on the Moon, and how were basin ejecta distributed on the lunar surface? (subprojects A1, A4, C4)
  4. What are the accurate absolute model ages of lunar basins derived from an improved lunar production function, and how does this compare to the chronology of lunar impactites and the lunar crust? (subprojects A2, A1, A5)
  5. Are morphologies of basins on Mercury consistent with our lunar-based models of basin formation, and are crater records on Mercury consistent with models of the size distribution of the impactor population(s) and the timing of the inner solar system’s impactor flux? (subproject A6)