Jupiter's Galilean Satellites
Melissa A. McGrath
NASA Marshall Space Flight Center

Jupiter's Galilean satellites Io, Europa, Ganymede and Callisto
encompass some of the most bizarre environments known in the solar
system, spanning that of Io, the most volcanically active and perhaps
the most inhospitable body known, to Europa, currently the focus of a
search for life in the solar system because of its subsurface ocean.
One of the premier areas of scientific return in solar system research
in the past 10 years, due in large part to the Galileo mission and
observations by the Hubble Space Telescope, has been a remarkable
increase in our knowledge about these satellites.  Discoveries have
been made of tenuous molecular oxygen atmospheres on Europa and
Ganymede, a magnetic field and accompanying auroral emissions at the
poles of Ganymede, and of ozone and sulfur dioxide embedded in the
surfaces of Europa, Ganymede and Callisto. Io's unusual sulfur dioxide
atmosphere, including its volcanic plumes and strong electrodynamic
interaction with magnetospheric plasma, has finally been quantitatively
characterized. This talk will present highlights from the recent
discoveries and advances in our understanding of these fascinating
objects.