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Origin of the cataclysmic Late Heavy Bombardment
period of the terrestrial planets
R. Gomes, H. F. Levison, K. Tsiganis & A. Morbidelli
The petrology record on the Moon suggests that a cataclysmic
spike in the cratering rate occurred ,700 million years after the
planets formed1; this event is known as the Late Heavy Bombardment
(LHB). Planetary formation theories cannot naturally
account for an intense period of planetesimal bombardment so
late in Solar System history. Several models have been proposed
to explain a late impact spike, but none of them has been set
within a self-consistent framework of Solar System evolution.
Here we propose that the LHB was triggered by the rapid
migration of the giant planets, which occurred after a long
quiescent period. During this burst of migration, the planetesimal
disk outside the orbits of the planets was destabilized, causing a
sudden massive delivery of planetesimals to the inner Solar
System. The asteroid belt was also strongly perturbed, with
these objects supplying a significant fraction of the LHB impactors
in accordance with recent geochemical evidence. Our model
not only naturally explains the LHB, but also reproduces the
observational constraints of the outer Solar System.