[meteorite-list] Impact-Generated Dust Clouds Surrounding the Galilean Moons

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:13:10 2004
Message-ID: <200304251540.IAA24692_at_zagami.jpl.nasa.gov>

Astrophysics, abstract
astro-ph/0304381

From: Harald Krueger <harald.krueger_at_mpi-hd.mpg.de>
Date: Tue, 22 Apr 2003 14:54:55 GMT (164kb)

Impact-Generated Dust Clouds Surrounding the Galilean Moons

Authors: Harald~Krüger, Alexander V. Krivov, Miodrag Sremcevi\'c, Eberhard Grün
Comments: Icarus, in press, 46 pages, 16 figures, 5 tables

Tenuous dust clouds of Jupiter's Galilean moons Io, Europa, Ganymede and Callisto
have been detected with the in-situ dust detector on board the Galileo spacecraft.
The majority of the dust particles have been sensed at altitudes below five radii
of these lunar-sized satellites. We identify the particles in the dust clouds
surrounding the moons by their impact direction, impact velocity, and mass
distribution. Average particle sizes are 0.5 to $\rm 1 \mu m$, just
above the detector threshold, indicating a size distribution with decreasing
numbers towards bigger particles. Our results imply that the particles have been
kicked up by hypervelocity impacts of micrometeoroids onto the satellites'
surfaces. The measured radial dust density profiles are consistent with
predictions by dynamical modeling for satellite ejecta produced by interplanetary
impactors (Krivov et al., PSS, 2003, 51, 251--269), assuming yield, mass and
velocity distributions of the ejecta from laboratory measurements. The dust
clouds of the three outer Galilean moons have very similar properties and are in
good agreement with the model predictions for solid ice-silicate surfaces. The
dust density in the vicinity of Io, however, is more than an order of magnitude
lower than expected from theory. This may be due to a softer, fluffier surface
of Io (volcanic deposits) as compared to the other moons. The log-log slope of
the dust number density in the clouds vs. distance from the satellite center
ranges between --1.6 and --2.8. Appreciable variations of number densities
obtained from individual flybys with varying geometry, especially at
Callisto, might be indicative of leading-trailing asymmetries of the clouds
due to the motion of the moons with respect to the field of impactors.
Received on Fri 25 Apr 2003 11:40:31 AM PDT