22 research outputs found
Jupiter's Moment of Inertia: A Possible Determination by JUNO
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 Lense-Thirring 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 Radau-Darwin 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 & Canup, 2006, ApJ, 640, L91) 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.Comment: accepted for publication in Icaru