Galileo Magnetometer Measurements: A Stronger Case for a Subsurface Ocean at Europa
Margaret G. Kivelson,*
Krishan K. Khurana,
Christopher T. Russell,
Martin Volwerk,
Raymond J. Walker,
Christophe Zimmer
On 3 January 2000, the Galileo spacecraft passed close
to Europa when it was located far south of Jupiter's magnetic equator in a region where the radial component of the magnetospheric magnetic field points inward toward Jupiter. This pass with a previously unexamined orientation of the external forcing field distinguished between an induced and a permanent magnetic dipole moment model of
Europa's internal field. The Galileo magnetometer measured changes in
the magnetic field predicted if a current-carrying outer shell, such as
a planet-scale liquid ocean, is present beneath the icy surface. The
evidence that Europa's field varies temporally strengthens the
argument that a liquid ocean exists beneath the present-day surface.
Institute of Geophysics and Planetary Physics, University of
California, Los Angeles, CA 90095-1567, USA.
*
To whom correspondence should be addressed. E-mail:
mkivelson{at}igpp.ucla.edu
