The cameras aboard Voyager 1 have provided a closeup view of the Jupiter system, revealing heretofore unknown characteristics and phenomena associated with the planet's atmosphere and the surfaces of its five major satellites. On Jupiter itself, atmospheric motions-the interaction of cloud systems-display complex vorticity. On its dark side, lightning and auroras are observed. A ring was discovered surrounding Jupiter. The satellite surfaces display dramatic differences including extensive active volcanism on Io, complex tectonism on Ganymede and possibly Europa, and flattened remnants of enormous impact features on Callisto.

The jupiter system through the eyes of voyager 1.

The origin and evolution of the solar system are analyzed. Physical processes are first discussed, followed by experimental studies of plasma-solid reactions and chemical and mineralogical analyses of meteorites and lunar and terrestrial samples.

Evolution of the Solar System

Near-infrared spectra of the Galilean satellites - Observations and compositional implications

The combination of the Doppler data from the first two Juno science orbits provides an improved estimate of the gravity field of Jupiter, crucial for interior modeling of giant planets The low-degree spherical harmonic coefficients, especially J4 and J6, are determined with accuracies better than previously published by a factor of 5 or more In addition, the independent estimates of the Jovian gravity field, obtained by the orbits separately, agree within uncertainties, pointing to a good stability of the solution The degree 2 sectoral and tesseral coefficients, C2,1, S2,1, C2,2, and S2,2, were determined to be statistically zero as expected for a fluid planet in equilibrium

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Jupiter gravity field estimated from the first two Juno orbits

A theoretical model is presented for the plasma in the Jovian magnetosphere whose pressure is comparable to the corotational energy density. The model predicts a thin current sheet of 1 Jupiter radius to 2 Jupiter radii half-thickness. The current sheet lies almost precisely in the magnetic equatorial plane and is not appreciably warped as suggested previously.

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The current sheet in Jupiter's magnetosphere

Two-way Doppler data received from Pioneer 10 during its encounter with Jupiter have been analyzed, and preliminary results have been obtained on the mass and the gravity field of Jupiter and on the masses of the four Galilean satellites. The ratios of the masses of the satellites to the mass of Jupiter are approximately 0.00004696 for Io, 0.00002565 for Europa, 0.00007845 for Ganymede, and 0.00005603 for Callisto (all error estimates presented in this paper are standard errors; those for Pioneer 10 represent our evaluation of the real errors as distinguished from formal errors). The ratio of the mass of the sun to the mass of the Jupiter system is about 1047.342, which is in good agreement with recent determinations from the motions of asteroids. The second- and fourth-degree zonal harmonic coefficients in the gravity field of Jupiter are 0.014720 and -0.00065, respectively, based on an equatorial planetary radius of 71,400 km, and the derived dynamical oblateness is 0.0647 at the same radius. The Pioneer 10 data are consistent with the assumption that Jupiter is in hydrostatic equilibrium at all levels.

J. D. Anderson

Papers

Gravity results from Pioneer 10 Doppler data