A tenuous dust ring of Jupiter formed by escaping ejecta from the Galilean satellites

Abstract

[1] This paper focuses on the dust environment between the orbits of the Galilean moons of Jupiter. Recent discovery of dust clouds around the Galilean satellites formed by impact ejecta from hypervelocity impacts of interplanetary micrometeoroids [Krüger et al., 1999d] suggests that a fraction of the ejected particles may escape from the source satellites into circum-Jovian orbits. We estimate production rates and study dynamical evolution of the escaping ejecta, controlled by gravitational, radiation pressure, and electromagnetic forces, to show that grains larger than several tenths of a micrometer in radius are likely to stay in bound orbits around Jupiter for tens or hundreds of years until they either are lost to collisions with the satellites or Jupiter or are ejected to interplanetary space. It is concluded that these small debris form a broad dust ring with number densities up to $10 3 km À3 , extending at least from Europa's orbit outward beyond the orbit of Callisto. Our results are consistent with in situ measurements of the Galileo spacecraft. We analyze impact events recorded by the Galileo dust detector from 1996 through 2001 and find more than 200 events outside the orbit of Europa, compatible with impacts of particles orbiting Jupiter in prograde orbits. An empirical dust number density distribution derived from these data agrees quite well with the theoretical one.

Dust on the Outskirts of the Jovian System

“…The radial profile of dust number density is nearly flat between about 50 and 300 jovian radii, with the absolute number density level of ∼10 km −3 (uncertain by a factor of 2 or 3). This is by two orders of magnitude less than the density of dust near the Europa orbit and by a factor of 10 less than the dust density at Callisto's orbit (∼10 3 km −3 and ∼10 2 km −3 , respectively; see Krivov et al 2002), yet an order of magnitude more that in the nearby interplanetary space.…”

“…The overwhelming majority of the remaining events took place closer to Jupiter in the region of the Galilean satellites. The data set includes impacts of tiny high-speed stream particles , electromagnetically captured interplanetary grains (Colwell et al 1998), dust grains of the clouds around the Galilean satellites (Krüger et al 1999c, grains that build up a tenuous dust ring between the orbits of Europa and Callisto (Krivov et al 2002), and possibly dust left from the fragmentation of the Shoemaker-Levy 9 (SL9) comet (Horányi 1994). We shall sift out all these, as well as interplanetary and interstellar dust impacts, and seek the dust impacts in the outermost part of the jovian system that may be compatible with impacts of particles in bound orbits about Jupiter produced by sources, which we later identify with outer irregular moons.…”

“…The noise could be removed from the class 2 data in this region (Krüger et al 1999b), but the lower classes 0 and 1 are noise events to almost 100%. This is the reason why other studies of the Jupiter dust environment (e.g., Krüger et al 2000, Thiessenhusen et al 2000, Krivov et al 2002, Krüger et al 2001) used the events with CLN = 3 and CLN = 2 only. On the contrary, beyond 20R J , the noise contamination in classes 0, 1, and 2 is very low, especially in the higher ion amplitude ranges AR ≥ 2.…”

“…In the jovian system, two gossamer rings are maintained through the impact ejection mechanism by four innermost satellites . Krivov et al (2002) argue for the existence of an extremely tenuous ring encompassing the orbits of the Galilean moons. Here we propose that an even more tenuous, yet detectable by in-situ measurements, dust cloud is associated with the outer irregular satellites.…”

Constraints from deuterium on the formation of icy bodies in the Jovian system and beyond

“…Krivov et al 2002;Krüger et al 2003Krüger et al , 2006. Collection of this dust by a spacecraft would therefore enable us to study the f -value present in the ices of these worlds.…”