HR: 1330h
AN: P12A-1051    [PDF]
TI: Detecting Current Geological Activity on the Galilean Satellites
AU: * Phillips, C B
EM: phillips@seti.org
AF: SETI Institute, 2035 Landings Drive, Mountain View, CA 94043 United States
AU: Chyba, C F
EM: chyba@seti.org
AF: SETI Institute, 2035 Landings Drive, Mountain View, CA 94043 United States
AB: The Galilean satellites have provided varying evidence for current, or recent, geological activity. Surface change on volcanic Io is frequent and widespread, while Europa's young surface and potential subsurface ocean layer indicate recent activity which could extend to the present day. Ganymede and Callisto have more ancient surfaces, but the detection of possible ocean layers beneath their icy surfaces suggests that ongoing geological activity cannot be ruled out. A number of methods are available to search for and characterize current geological activity, and such observations should be carried out by any upcoming mission to the Jovian system such as JIMO. 1) Change detection: Comparisons of images of the same portion of the surfaces of the satellites, taken on subsequent orbits or missions, can be used to search for differences due to geological activity (Phillips et al. 2000 JGR 105, 22579). Effective comparisons require filters at comparable wavelengths and bandpasses to Galileo (and perhaps Voyager), and images of regions observed by Galileo taken at the same phase angle, wavelength, and resolution. Such observations can monitor ongoing volcanic activity on Io, even from distant imaging taken while orbiting other satellites. These images should be optimized at Europa, but it is worth studying images of Ganymede and Callisto as well, especially at higher resolutions, to see if any changes have taken place since Galileo or Voyager. 2) Plume searches: High-resolution imaging sequences at locations where periodic stresses favor plume activity, as well as global-scale images including the limb of the planet, can be used to search for plume activity on Europa. Regular plume monitoring can also be used to observe volcanic activity on Io. An orbiting spectrometer could look for particular outgassed constituents from the satellites, and monitoring of the space environment surrounding Europa by charged particle detectors on a future mission could allow detection of plume activity by searching for enhancements in the gas torii surrounding the satellites. 3) Thermal anomalies: Visible and IR imaging may be able to detect thermal anomalies due to intrusions of warm water / ice for hundreds of years on Europa, and larger-scale thermal plumes could leave areas of thinner crust for up to 1 Myr. that could be detected by radar sounding. Thermal imaging of Io can reveal information about the heat flow at Io's volcanoes, and should be performed for Europa as well as Ganymede and Callisto to look for localized thermal anomalies.
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6218 Jovian satellites
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting