Ice Grain Size Distribution: Differences Between Jovian and Saturnian Icy Satellites From Galileo and Cassini Measurements

HR: 0800h
AN: P11B-0124 [Abstracts]
TI: Ice Grain Size Distribution: Differences Between Jovian and Saturnian Icy Satellites From Galileo and Cassini Measurements
AU: * Hansen, G
EM: ghansen@rad.ess.washington.edu
AF: Univ. Washington, Dept. Earth and Space Sci. Box 351310, Seattle, WA 98195
AU: McCord, T
EM: mccordtb@aol.com
AF: Space Science Inst., NW Division, 22 Fiddler's Road PO Box 667, Winthrop, WA 98862
AU: Clark, R
EM: rclark@usgs.gov
AF: US Geological Survey, Mail Stop 964 Box 25046 Denver Federal Center, Denver, CO 80225
AU: Cruikshank, D
EM: Dale.P.Cruikshank@nasa.gov
AF: Ames Research Center, Astrophysics Branch Mail Stop 245-6, Moffett Field, CA 94035
AU: Brown, R
EM: rhb@lpl.arizona.edu
AF: Univ. Arizona, Dept. of Planetary Sci. Lunar and Planetary Lab. 1629 E. University Blvd., Tucson, AZ 85721
AU: Baines, K
EM: kbaines@pop.jpl.nasa.gov
AF: Jet Propulsion Lab., 4800 Oak Grove Dr., Pasadena, CA 91109
AU: Bellucci, G
EM: giancarlo.bellucci@ifsi.rm.cnr.it
AF: IFSI, Area Ricerca CNR Tor Vergata Via Fosso del Cavaliere, Rome, 00133 Rome Italy
AU: Buratti, B
EM: bonnie.j.buratti@jpl.nasa.gov
AF: Jet Propulsion Lab., 4800 Oak Grove Dr., Pasadena, CA 91109
AU: Capaccoini, F
EM: capaccio@saturn.ias.rm.cnr.it
AF: IAS, Area Ricerca CNR Tor Vergata Via Fosso del Cavaliere, Rome, 00133 Rome Italy
AU: Cerroni, P
EM: priscio@ias.rm.cnr.it
AF: IAS, Area Ricerca CNR Tor Vergata Via Fosso del Cavaliere, Rome, 00133 Rome Italy
AU: Combes, M
EM: michel.combes@obspm.fr
AF: l'Obs. de Paris, Dept De Recherche Spatial 5 place Jules Janssen, Meudon Principal Ced, 92195 France
AU: Coradini, A
EM: coradini@ias.rm.cnr.it
AF: IAS, Area Ricerca CNR Tor Vergata Via Fosso del Cavaliere, Rome, 00133 Rome Italy
AU: Drossart, P
EM: Pierre.Drossart@obspm.fr
AF: DLR, Rutherfordstrasse 2, Berlin, D-12489 Germany
AU: Formisano, V
P11B-0124 AF: IFSI, Area Ricerca CNR Tor Vergata Via Fosso del Cavaliere, Rome, 00133 Rome Italy
AU: Jaumann, R
EM: formisan@nike.ifsi.rm.cnr.it
AF: DLR, Rutherfordstrasse 2, Berlin, D-12489 Germany
AU: Langevin, Y
EM: yves.langevin@ias.fr
AF: IAS, Bat. 121 91405 Orsay Campus, Orsay, 91405 France
AU: Matson, D
EM: Dennis.L.Matson@jpl.nasa.gov
AF: Jet Propulsion Lab., 4800 Oak Grove Dr., Pasadena, CA 91109
AU: Mennella, V
EM: mennella@na.astro.it
AF: INAF, Obs. Astron. di Capodimonte Via Moiariello 16, Napoli, 80131 Italy
AU: Nelson, R
EM: robert.m.nelson@jpl.nasa.gov
AF: Jet Propulsion Lab., 4800 Oak Grove Dr., Pasadena, CA 91109
AU: Nicholson, P
EM: nicholson@astrosun.tn.cornell.edu
AF: Cornell Univ., 418 Space Sci. Bldg., Ithaca, NY 14853
AU: Sicardy, B
EM: bruno.sicardy@obspm.fr
AF: DLR, Rutherfordstrasse 2, Berlin, D-12489 Germany
AU: Sotin, C
EM: sotin@chimie.univ-nantes.fr
AF: LPG, Univ. Nantes, Faculte des Sciences B.P. 92208 2 rue de la Houssiniere, Nantes Cedex 3, 44072 France
AU: Soderblom, L
EM: lsoderblom@usgs.gov
AF: US Geological Survey, 2255 N. Gemini Dr., Flagstaff, AZ 86001
AU: Hibbitts, C
EM: hibbitts@psi.edu
AF: Applied Physics Lab., Johns Hopkins Univ. 11100 Johns Hopkins Road, Laurel, MD 20723
AB: Most of the satellites of the outer solar system have surfaces substantially covered by water ice, whose near-infrared (1-5 μm) spectrum has absorption bands near 1.05, 1.25, 1.5, and 2.0 μm, and a strong broad absorption beyond 3 μm. For fine-grained ice, a reflection peak near 3.6 μm occurs. For grain sizes larger than a micrometer, a Fresnel reflection peak appears near 3.1 μm. The reflection spectrum of the icy Galilean satellites of Jupiter (Callisto, Ganymede and Europa), as returned by the Galileo Near Infrared Mapping Spectrometer, are well fit by ice models using a single, or at most a closely-spaced bimodal, grain size in the range from 10 to several 100 μm, depending on satellite and location. These spectra all have a strong 3.1-μm peak. The reflection spectrum of the Saturnian icy satellites Mimas, Tethys, Rhea, Enceladus, Dione, and the icy hemisphere of Iapetus was returned by the Cassini Visual and Infrared Mapping Spectrometer instrument. They are are very different, consistent with grain sizes ranging from 1 to 5 μm, comparable to telescopic observations over the last two decades. The 3.1-μm reflection peak is also often muted or indistinct and is generally small at high phase angles. This behavior can be modeled as a coarse-sized distribution covered by purely absorbing sub-micron grains. We know that the radiation environment is much stronger in the Jovian system, and this is perhaps the cause of the coarse-grained (0.5-1 mm) ice seen on the trailing sides of Europa and Ganymede. All the Galilean satellites surfaces show recent evolution, including resurfacing on Europa and volatile-driven mass wasting on Callisto, and can experience thermal grain coarsening more readily at the higher Jovian temperatures. The grain sizes on the Saturnian satellites may indicate much older surfaces in a different thermal and radiation environment that results in an undisturbed deposit of micrometeorite gardened micron to sub-micron grains.
DE: 5422 Ices
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
DE: 6280 Saturnian satellites
SC: Planetary Sciences [P]
MN: Fall Meeting 2005