A mascon approach to estimating the depth of Jupiter’s Great Red Spot with Juno gravity measurements

Abstract

We evaluate a method for determining the depth of Jupiter’s Great Red Spot (GRS) with two Juno overflights dedicated to gravity science. The small-scale, localized nature of the anticyclone requires a detection method where the gravity perturbations are regional. To this end, we model the GRS as a dipole of flat disk mass concentrations (mascons), separated along the radial direction of Jupiter. Thermal wind theory predicts such structure composed of two equal and opposite masses below the visible cloud tops, condition that is used to constrain our estimation algorithm. Furthermore, Juno radiometer observations of the GRS brightness temperature indicate the presence of anomalies of opposite sign at different depths. We present the results of both a covariance and recovery analyses of the simulated data, in terms of accuracy in the estimation of the GRS mass and depth of winds. The analyses are carried out using precise Doppler tracking of the Juno spacecraft and by posing constraints on the interior model of the vortex from theory. We find that, if the surface dynamics extend at least several hundred kilometers below the cloud tops, it is possible to resolve the mass concentrations using both gravity passes, and tie the mass to the vortex’s depth through thermal wind.