Damping of Terrestrial‐Planet Eccentricities by Density‐Wave Interactions with a Remnant Gas Disk

We examine the damping of terrestrial-planet eccentricities via density-wave interactions with a remnant gas disk that postdated the accretionary epoch. A lower limit is estimated for the gas surface density present in the terrestrial zone required for acoustic damping to be effective, and a simple model for describing the disk's influence on the planet eccentricities is presented. The results suggest that the terrestrial-planet eccentricities could be reduced from values permitting crossing orbits to the present-day values by a remnant disk with gas surface density of ~10 -3 -10 -4 times the minimum-mass solar nebula value and characteristic gas dissipation timescales of 10 6 -10 7 yr.