636 Encyclopedia of the Solar System
extrasolar systems will bring new insights to zodiacal clouds
around other stars.
Interplanetary space missions presently under way that
carry dust detectors are theUlyssesandCassinimissions.
Ulysseshas probed the space above the poles of the Sun
and outside 1 AU and continues its study of the interplan-
etary dust cloud at times of high solar activity.Galileoand
Cassinihad become the first man-made satellites of Jupiter
and Saturn, respectively, and are studying their dust envi-
ronments. The detailed study of cometary and interstellar
dust is the goal of NASA’sStardustmission, which returned
samples of dust from Comet Wild 2 in early 2006. The
JapaneseHyabusamission collected dust from Asteroid
Itokawa and is on its return to Earth. The European Space
Agency’sRosettamission will follow Comet Churyumov
Gerasimenko through its perihelion and investigate its re-
lease of dust to interplanetary space.
Dust particles, like photons, are born at remote sites
in space and time, and carry from there information that
may not be accessible to direct investigation. From knowl-
edge of the dust particles’ birthplace and the particles’ bulk
properties, we can learn about the remote environment
out of which the particles were formed. This approach
is called dust astronomy and is carried out by means of
dust telescopes on dust observatories in space. Targets for
dust telescopes are dust from the local interstellar medium,
cometary, asteroidal dust, and space debris. Dust particles’
trajectories are determined by the measurements of the
electric charge signals that are induced when the charged
grains fly through charge-sensitive grid systems. Modern in
situ dust detectors are capable of providing mass, speed, and
physical and chemical information of dust grains in space. A
dust telescope can, therefore, be considered as a combina-
tion of detectors for dust particle trajectories along with de-
tectors for physical and chemical analysis of dust particles.
Both dust trajectory sensors and large-area dust analyzers
have been developed recently and await their use in space.
In near-Earth space, ambitious new techniques will be
applied to collect meteoritic material that is not accessible
by other methods. High-speed meteoroid catchers, which
permit the determination of the trajectory as well as the
recovery of material for analysis in ground laboratories, are
under development. A cosmic dust collector is currently
being flown on the International Space Station (ISS).
Laboratory studies are instrumental in improving our
understanding of planetary and interplanetary processes in
which dust plays a major role. The study of dust–plasma
interactions is a new and expanding field that is attracting
considerable attention. New phenomena are expected to
occur when plasma is loaded with large amounts of dust.
Processes of this type are suspected to play a significant
role in cometary environments, in planetary rings, and in
protoplanetary disks.Bibliography
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