HR: 16:00h
AN: G42C-01 INVITED [PDF]
TI: Geodesy of Amalthea and the Galilean Satellites of Jupiter
AU: * Schubert, G
EM: schubert@ucla.edu
AF: Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095-1567 United States
AU: Anderson, J D
EM: John.D.Anderson@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA
91109-8099 United States
AU: Jacobson, R A
EM: Robert.A. Jacobson@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA
91109-8099 United States
AU: Lau, E L
EM: Eunice.L.Lau@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA
91109-8099 United States
AU: Moore, W B
EM: bmoore@avalon.ess.ucla.edu
AF: Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095-1567 United States
AU: Palguta, J
EM: jpalguta@ucla.edu
AF: Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, 595 Charles E. Young Drive East, Los Angeles, CA 90095-1567 United States
AB:
An important scientific legacy of the Galileo
mission is the determination of the masses
and quadrupole components of the gravitational fields
of the Galilean satellites. A final report of
the mission results is given including values of
$GM\/$ ($G\/$ is the universal gravitational constant,
$M\/$ is satellite mass), the gravitational coefficients
$J_2$ and $C_{22}$, and the correlation coefficient
$\mu\/$ between $J_2$ and $C_{22}$. The values of
$J_2$ and $C_{22}$ are deduced using the {\em a priori\/}
assumption $J_2 = (10/3)\/C_{22}$. The least squares
method for fitting the Doppler residuals does not fix
this ratio, but allows $J_2$ and $C_{22}$ to vary
independently and determines the correlation
between them. The {\em a priori\/} assumption is consistent with the hydrostatic equilibrium of a satellite, but it
does not require hydrostaticity. Values of
$\mu\/$ show that $J_2$ and $C_{22}$ are
independently determined only for Io; the
ratio of $J_2$ and $C_{22}$ is consistent with
a hydrostatic Io. $J_2$ and $C_{22}$ are not
independently determined for Ganymede even though there are both equatorial and polar flybys of the satellite.
A quadrupole field is insufficient to fit the
Ganymede data to the noise level. The additional signal is
interpreted in terms of mascon anomalies at
the surface of Ganymede. The gravitational
coefficients, together with the assumption that the degree~2
gravitational fields of the satellites derive from their
hydrostatic distortions to rotation and the Jovian
tidal force, are used to infer the moments of
inertia of the satellites and their internal
structures. The mass and closest approach distance
for Amalthea can be determined from Doppler data from the
Galileo encounter of 5~November 2002. The final results
indicate a density that is significantly smaller
than the approximate $1000~\mbox{kg\ m}^{-3}$ density of water ice. The quadrupole components of Amalthea's
gravitational field are undetectable in the encounter Doppler data.
DE: 1227 Planetary geodesy and gravity (5420, 5714, 6019)
DE: 5417 Gravitational fields (1227)
DE: 5430 Interiors (8147)
DE: 6218 Jovian satellites
SC: Geodesy [G]
MN: 2003 Fall Meeting