31st Annual Meeting of the DPS, October 1999
Session 36. Planet Formation: Solar Nebula
Contributed Oral Parallel Session, Wednesday, October 13, 1999, 10:30am-12:00noon, Sala Kursaal

[Previous] | [Session 36] | [Next]

[36.04] Resonant Interaction of the Moon with its Precursor Disk

R. M. Canup, Wm. R. Ward (Southwest Research Institute)

In the impact hypothesis of lunar formation, a close circumterrestrial disk ( ~ 2-3RE) yields a lunar-sized Moon. An initial disk mass of at least two-lunar masses is implied by conservation of angular momentum, which dictates that close to half the disk must be sacrificed to the Earth in order for the remaining material to spread beyond the Roche limit where accretion of the Moon can occur ( e.g., Ida et al. 1997). The collision time scale for objects outside the Roche limit is typically much shorter than the radiation-limited lifetime of the protolunar disk (Thompson and Stevenson 1988), suggesting that a newly-formed Moon may co-exist with its interior precursor disk for a time interval O(102) years.

The Moon can dynamically couple to this disk through resonant interactions. These can be quite powerful, and can rapidly modify the orbital radius, eccentricity, and inclination. It is likely that the disk torques are much larger than those due to terrestrial tides, and thus control the rate of early outward migration of the Moon. They may also establish the intial conditions for the subsequent tidal evolution of the Earth-Moon system (e.g. Goldreich 1966, Touma and Wisdom 1994).

[Previous] | [Session 36] | [Next]