Jupiter’s moment of inertia: A possible determination by Juno
Abstract
The moment of inertia of a giant planet reveals important information about the planet’s internal density structure and this information is not identical to that contained in the gravitational moments. The forthcoming Juno mission to Jupiter might determine Jupiter’s normalized moment of inertia NMoI = C/MR^{2} by measuring Jupiter’s pole precession and the LenseThirring acceleration of the spacecraft (C is the axial moment of inertia, and M and R are Jupiter’s mass and mean radius, respectively). We investigate the possible range of NMoI values for Jupiter based on its measured gravitational field using a simple core/envelope model of the planet assuming that J_{2} and J_{4} are perfectly known and are equal to their measured values. The model suggests that for fixed values of J_{2} and J_{4} a range of NMoI values between 0.2629 and 0.2645 can be found. The RadauDarwin relation gives a NMoI value that is larger than the model values by less than 1%. A low NMoI of ∼0.236, inferred from a dynamical model (Ward, W.R., Canup, R.M. [2006]. Astrophys. J. 640, L91L94) is inconsistent with this range, but the range is model dependent. Although we conclude that the NMoI is tightly constrained by the gravity coefficients, a measurement of Jupiter’s NMoI to a few tenths of percent by Juno could provide an important constraint on Jupiter’s internal structure. We carry out a simplified assessment of the error involved in Juno’s possible determination of Jupiter’s NMoI.
 Publication:

Icarus
 Pub Date:
 December 2011
 DOI:
 10.1016/j.icarus.2011.09.016
 arXiv:
 arXiv:1109.1627
 Bibcode:
 2011Icar..216..440H
 Keywords:

 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 accepted for publication in Icarus