...............Conclusions

• The young basins represent an epoch of late (~700My) heavy bombardment of the Moon
• There has been controversy of whether these basins represent:
  1. The tail end of terrestrial planet accretion.
  2. A spike in the impact rate.
• Based on dynamical simulation, Bottke et al. (2007) argued that it is unlikely to be (1).
  • It would be useful if this were confirmed with real data.
• If spike, then the orbits of the planets had to change at 3.9Ga.
  • The Nice model is the most successful to date at explaining the LHB observations.
    • LHB caused a dynamical instability in the orbits of Uranus and Neptune.
    • It can also explain many of the characteristics of the outer Solar System.

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This talk can be found at www.boulder.swri.edu/~hal/talks.html
We are grateful to NASA's NSLI, Origins, and OPR programs for support. ...............