Quarles, Billy - Theia's provenance: dynamical evolution of a late Impactor

Abstract: 
In the Solar System's early history many processes have been proposed that depend on the dynamical state of the planets.  Our study considers the possible dynamical states that produce a late Giant Impact (70 – 110 Myr) to form the Earth-Moon system.  We investigate within the semimajor axis and eccentricity parameter space to determine the possible outcomes of a 5 terrestrial planet model of the Solar System for 3 different mass ratios (8:1, 4:1, and 1:1) of the Earth-Moon progenitors.  Using angular momentum conservation, an initial condition is prescribed  for the progenitor masses while using initial conditions for the other Solar System bodies from a well-known common epoch.  Additionally we test the 4:1 mass ratio with a different giant planet configuration akin to the Nice model.

We find local regions of our parameter space are more conducive to the outcome of a late Giant Impact.  Mean motion resonances (MMRs) are identified between the terrestrial planets and used along with secular effects from the giant planets to indicate likely regions where a Giant Impact would occur.  We characterize our results considering the estimated time of the Giant Impact, the resultant mass distribution of terrestrial planets, and the post collision mean angular momentum deficit (AMD).  Case studies are presented illustrating the various possible outcomes with respect to their AMD relative to the current Solar System.  Our statistical results show that a Nice model giant planet configuration can affect the occurrence of Giant Impacts and a restricted region of parameter space exists for all considered cases.  The implications on planet formation scenarios and implicit habitability will also be discussed.