Impact of Comet Shoemaker–Levy 9—Size, Origin, and Plumes: Comparison of Numerical Analysis with Observations

Abstract

Numerical results of impact of Comet Shoemaker–Levy 9 (SL9) on Jupiter are compared with observational phenomena to investigate the size and origin of SL9 and impact features. Plume evolution is simulated numerically for 0.4- and 2.0-km-diameter (D) impactors. Analytical estimates indicate that the maximum plume heights are proportional to (D/lnD)^3. This relation is also confirmed by the extrapolation of numerical simulations. From the correlation between maximum plume heights and impactor diameters, the diameters of large SL9 fragments and the parent body are estimated as ∼2 and 4–5 km, respectively. The plume induced by the impact of fragments of SL9 consists of atmospheric gas and impactor material. The chemical abundances of the plumes, especially their high CO abundances, indicate that they contain primitive materials from fragments and thus SL9 is probably of cometary origin. The lateral expansion of plume is also examined. Our simulations suggest that the energy source required to produce the observable waves should be located in the stratospheric region, rather than in the deep troposphere. Finally, the ejecta pattern observed by Hubble Space Telescope [Hammel et al. (1995) Science 267, 1288–1296] is simulated by a simple particle model. The results suggest that the ejection of atmospheric gas and cometary materials from a narrow ∼30° cone region along the trajectory spreads out and yields the ejecta patterns observed by Hubble Space Telescope overlying the clouds.