Jupiter's obliquity and a long-lived circumplanetary disk

Abstract

It has been claimed [Canup, R.M., Ward, W.R., 2002. Astron. J. 124, 3404–3423; Ward, W.R., 2003. In: AGU, Fall Meeting 2003] that a long-lived minimum mass circumplanetary gas disk is inconsistent with Jupiter's low obliquity. Here we find that while Jupiter's obliquity may constrain its characteristics it does not rule out a long-lived massive (compared to the mass of the Galilean satellites) disk. This is because the argument assumes a Solar System much like that of the present day with the one exception of a circumjovian disk which is then allowed to dissipate on a long timescale ( 10 6 – 10 7 yr ). Given that the sequence of events in Solar System history that fit known constraints is non-unique, we choose for the sake of clarity of exposition the orbital architecture framework of Tsiganis et al. [Tsiganis, K., Gomes, R., Morbidelli, A., Levison, H.F., 2005. Nature 435, 459–461], in which Jupiter and Saturn were once in compact, nearly coplanar orbits, and show that in this case Jupiter's low obliquity is consistent with the SEMM (solids-enhanced minimum mass) satellite formation model of Mosqueira and Estrada [Mosqueira, I., Estrada, P.R., 2003a. Icarus 163, 198–231; Mosqueira, I., Estrada, P.R., 2003b. Icarus 163, 232–255]. We suggest that a low inclination starting condition may apply, but stress that our SEMM satellite formation model could be compatible with Jupiter's obliquity even for mutually inclined giant planets.