Zusammenfassung
By successively orbiting both 4 Vesta and I Ceres the Dawn mission
directly addresses the long-standing goals of understanding the origin
and evolution of the solar system. Ceres and Vesta are two complementary
terrestrial protoplanets (one apparently "wet" and the other "dry"),
whose accretion was probably terminated by the formation of Jupiter.
They provide a bridge in our understanding between the rocky bodies
of the inner solar system and the icy bodies of the outer solar system.
Ceres appears to be undifferentiated while Vesta has experienced
significant heating and likely differentiation. Both formed very
early in the history of the solar system and while suffering many
impacts have remained intact, thereby retaining a record of events
and processes from the time of planet formation. Detailed study of
the geophysics and geochemistry of these two bodies provides critical
benchmarks for early solar system conditions and processes that shaped
its subsequent evolution. Dawn provides the missing context for both
primitive and evolved meteoritic data, thus playing a central role
in understanding terrestrial planet formation and the evolution of
the asteroid belt. Dawn is to be launched in May 2006 arriving at
Vesta in 2010 and Ceres in 2014, stopping at each to make I I months
of orbital measurements. The spacecraft uses solar electric propulsion,
both in cruise and in orbit, to make most efficient use of its xenon
propellant. The spacecraft carries a framing camera, visible and
infrared mapping spectrometer, gamma ray/neutron spectrometer, magnetometer,
and radio Science. (C) 2003 Elsevier Ltd. All rights reserved.
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