HR: 11:10h
AN: P11C-04 INVITED     [PDF]
TI: A Science Foundation for Orbital Subsurface Radar Sounding of Jupiter's Icy Moons
AU: * Blankenship, D D
EM: blank@ig.utexas.edu
AF: Univ. Texas, Inst. for Geophysics, 4412 Spicewood Springs Rd, Bldg 600, Austin, TX 78759
AU: Winebrenner, D P
EM: dpw@apl.washington.edu
AF: Univ. Washington, Polar Science Center, Seattle, WA 98105
AU: Campbell, B A
EM: campbell@nasm.si.edu
AF: Smithsonian Inst., National Air and Space Museum, Washington, DC 20560
AU: Pappalardo, R T
EM: robert.pappalardo@colorado.edu
AF: Univ. of Colorado, Lab. for Atmospheric and Space Phys., Boulder, CO 80309
AU: Sandwell, D T
EM: sandwell@geosat.ucsd.edu
AF: Univ. of California, Scripps Inst. of Oceanography, La Jolla, CA 92093
AB: A fundamental question for both science and society is the uniqueness of life within the solar system. Biology as we know it requires free water, heat, and a flux of chemical compounds. Beyond Earth, the recently identified sub-ice oceans of Europa, Ganymede and Callisto are believed to be the solar system's other significant concentrations of free water. At present we know little about the distribution of free water or the flux of chemical compounds within these moons' icy/watery outer shells. The proposed Jupiter Icy Moons Orbiter (JIMO) presents exciting prospects for addressing these issues. The subgroup for Orbital Subsurface Science of the JIMO Science Definition Team discussed these prospects with the broader scientific community at a forum held in June of 2003. At the forum it was concluded that the primary subsurface science objective is to determine the volumetric distribution of free water (including brines) within Europa, Ganymede and Callisto. This should be accomplished through a study of the subsurface thermal and kinematic factors that control the distribution of free water and how this distribution has changed through time; in addition, a study of the relationship between these factors and observed surface features was recommended. A second subsurface science objective is to determine the means of ice-ocean interchange of material on Europa and where this material could best be sampled by future landed missions. The recommendations here were to test the hypothesis of direct exchange between any ocean and the icy mantle's cold brittle shell and shallow subsurface; an additional recommendation was made to test the hypothesis of indirect exchange with any ocean through the movement of deep ductile ice into the cold brittle shell. A final objective is to determine the geologic processes that control the exchange of material in the shallow subsurface of the three moons. This would require studying the physical properties above the annealing depth and their relationship to the mapped distributions of surface constituents, physical structures and thermal features, as well as their relationship to deeper geological processes. Because ice is characterized by very low dielectric losses, it was recognized that these investigations could be accomplished by a combination of global and localized radar profiling of thermal, compositional and structural horizons within the three moons' icy shells. This profiling should be at two scales, targeting horizons at depths of up to 30 km at 100 m vertical resolution, and at depths of up to 2 km with 10 m vertical resolution. The global profiles were recommended to have equatorial separation of at least $5\deg$ and the targeted profiles would emphasize high-resolution studies of representative surface features. To fully understand geological processes in the shallow subsurface, a consensus was also reached that the subsurface ($>$ 1 m) heterogeneity of the regolith should be mapped at better than 100 m horizontal resolution over at least 50% of the surface of the three moons. The forum attendees also emphasized that the primary factors controlling the topography of Jupiter's icy moons are characterized by thermal, compositional and structural horizons that are likely to be detectable by electromagnetic probing. Suggested links between investigations of subsurface horizons and topography will also be presented.
DE: 5410 Composition
DE: 5430 Interiors (8147)
DE: 5709 Composition
DE: 6218 Jovian satellites
DE: 8149 Planetary tectonics (5475)
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting