AAS 199th meeting, Washington, DC, January 2002
Session 28. Solar System: Dynamics and Collisions
Oral, Monday, January 7, 2002, 10:00-11:30am, Jefferson East

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[28.02] Dynamical Evolution of the Earth-Moon Progenitors

E.J. Rivera (NASA/Ames)

In my Ph.D. dissertation, I explored the plausibility of having five terrestrial planets for 8 -- 200 Myr, having two of them collide in this time, and leaving a planetary system with small orbital eccentricities as in the Solar System. I performed 191 N-body simulations which started with the planets Mercury through Neptune with their current orbits and masses except that the Earth and Moon were replaced with two bodies (the Earth-Moon progenitors), each in its own heliocentric orbit between the orbits of Venus and Mars, such that mass and angular momentum were conserved. I varied the mass ratio of the Earth-Moon progenitors, their initial eccentricities, inclinations, and semi-major axes. When a collision occurred, the bodies were simply merged into one. Slightly over one-half of the simulations ended with a collision between two planets before 200 Myr had elapsed, and about one-third of the systems which started with five terrestrial planets were stable for 200 Myr. Out of the 191 simulations, 16 ended with a collision between the Earth-Moon progenitors in the right time interval; four of these 16 resulting systems resembled the Solar System in that the terrestrial planets were on nearly circular, coplanar orbits. An additional 27 simulations ended with a collision at the right time which left four terrestrial planets with a mass distribution similar to that in the Solar System. Four of these 27 resulting systems resembled the Solar System. Thus, the scenario I explored does seem plausible.

This research was supported in part by NASA's Origins of Solar Systems program under grant NAG 5-9680.

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