Chronology and Sources of Lunar Impact Bombardment
Matija \'Cuk

TL;DR
This paper investigates the lunar impact history, emphasizing the role of primordial Mars-crossers in shaping the Moon's cratering record and proposing a late impact spike caused by a disrupted large asteroid.
Contribution
It introduces a model linking Mars-crossers to lunar cratering and suggests a discrete impact event caused by a disrupted large asteroid.
Findings
Mars-crosser population initially decays with an 80-Myr half-life.
Primordial Mars-crosser population estimated at 0.01-0.02 Earth masses.
A late impact spike likely caused by a disrupted Vesta-sized body.
Abstract
The Moon has suffered intense impact bombardment ending at 3.9 Gyr ago, and this bombardment probably affected all of the inner Solar System. Basin magnetization signatures and lunar crater size-distributions indicate that the last episode of bombardment at about 3.85 Gyr ago was less extensive than previously thought. We explore the contribution of the primordial Mars-crosser population to early lunar bombardment. We find that Mars-crosser population initially decays with a 80-Myr half-life, with the long tail of survivors clustering on temporarily non-Mars-crossing orbits between 1.8 and 2 AU. These survivors decay with half-life of about 600 Myr and are progenitors of the extant Hungaria asteroid group in the same region. We estimate the primordial Mars-crosser population contained about 0.01-0.02 Earth masses. Such initial population is consistent with no lunar basins forming after…
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