Giant impacts in the Saturnian System: a possible origin of diversity in the inner mid-sized satellites

Abstract

It is widely accepted that Titan and the mid-sized regular satellites around Saturn were formed in the circum-Saturn disk. Thus, if these mid-sized satellites were simply accreted by collisions of similar ice-rock satellitesimals in the disk, the observed wide diversity in density (i.e., the rock fraction) of the Saturnian mid-sized satellites is enigmatic. A recent circumplanetary disk model suggests satellite growth in an actively supplied circumplanetary disk, in which Titan-sized satellites migrate inward by interaction with the gas and are eventually lost to the gas planet. Here we report numerical simulations of giant impacts between Titan-sized migrating satellites and smaller satellites in the inner region of the Saturnian disk. Our results suggest that in a giant impact with impact velocity > 1.4 times the escape velocity and impact angle of ~45 degree, a smaller satellite is destroyed, forming multiple mid-sized satellites with a very wide diversity in satellite density (the rock fraction = 0-92 wt%). Our results of the relationship between the mass and rock fraction of the satellites resulting from giant impacts reproduce the observations of the Saturnian mid-sized satellites. Giant impacts also lead to internal melting of the formed mid-sized satellites, which would initiate strong tidal dissipation and geological activity, such as those observed on Enceladus today and Tethys in the past. Our findings also imply that giant impacts might have affected the fundamental physical property of the Saturnian mid-sized satellites as well as those of the terrestrial planets in the solar system and beyond.

18 pages, 3 figures, Planetary and Space Science, in press

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Cited by in corpus (7)

• Warm Debris Disks Produced by Giant Impacts During Terrestrial Planet Formation
• Formation of moon systems around giant planets: Capture and ablation of planetesimals as foundation for a pebble accretion scenario
• Resolution Dependence of Disruptive Collisions between Planetesimals in the Gravity Regime
• Insights into planet formation from debris disks: II. Giant impacts in extrasolar planetary systems
• Collision Chains among the Terrestrial Planets. III. Formation of the Moon
• Distribution of captured planetesimals in circumplanetary gas disks and implications for accretion of regular satellites
• Collisional Disruption of Planetesimals in the Gravity Regime with iSALE Code: Comparison with SPH code for Purely Hydrodynamic Bodies