Exploring the role of the Sun's motion in terrestrial comet impacts
  The cratering record on the Earth and Moon shows that our planet has been
exposed to high velocity impacts for much or all of its existence. Some of
these craters were produced by the impact of long period comets (LPCs). These
probably originated in the Oort cloud, and were put into their present orbits
through gravitational perturbations arising from the Galactic tide and stellar
encounters, both of which are modulated by the solar motion about the Galaxy.
Here we construct dynamicalmodels of these mechanisms in order to predict the
time-varying impact rate of LPCs and the angular distribution of their
perihelia (which is observed to be non-uniform). Comparing the predictions of
these dynamical models with other models, we conclude that cometary impacts
induced by the solar motion contribute only a small fraction of terrestrial
impact craters over the past 250 Myr. Over this time scale the apparent
cratering rate is dominated by a secular increase towards the present, which
might be the result of the disruption of a large asteroid. Our dynamical
models, together with the solar apex motion, predict a non-uniform angular
distribution of the perihelia, without needing to invoke the existence of a
massive body in the outer Oort cloud. Our results are reasonably robust to
changes in the parameters of the Galaxy model, Oort cloud, and stellar
encounters.
