November 16, 2001
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. Galileo magnetometer observations have verified the presence of a subsurface ocean on Europa and 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.
Dr. Melissa A. McGrath is a member of the senior science staff at the Space Telescope Science Institute in Baltimore, which she joined in 1992. She received her B.A. in Physics & Astronomy from Mt. Holyoke College in 1977, and an M.A. and Ph.D in Astronomy from the University of Virginia in 1984 and 1987 respectively. From 1987-1992 she was a postdoctoral fellow and Associate Research Scientist in the Johns Hopkins University Department of Physics and Astronomy. Her research is in planetary sciences, and consists primarily of observational work with space-based telescopes performing imaging and spectroscopic studies of the Galilean satellites and the magnetospheres and upper atmospheres of the outer planets Jupiter, Saturn, Uranus and Neptune.