Dawn: A journey in space and time

Abstract

By successively orbiting both 4 Vesta and 1 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 11 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.3

Geochemistry of 4 Vesta based on HED meteorites: Prospective study for interpretation of gamma ray and neutron spectra for the Dawn mission

“…In addition to GRaND, the Dawn spacecraft is equipped with a VIR, which can identify some minerals on Vesta with higher spatial resolution than that of GRaND (Russell et al 2004). In particular, diagnostic absorption bands for olivine and pyroxenes occur in the visible and near-infrared regions.…”

“…Dawn, the ninth NASA Discovery mission, will orbit and explore two of the largest Main Belt asteroids, 4 Vesta and 1 Ceres, which are complementary protoplanets that have remained intact since their formation (Rayman et al 2006;Russell et al 2004). Vesta is highly differentiated and is thought to be the parent body for the voluminous howardite, eucrite, and diogenite (HED) suites (Binzel and Xu 1993;Keil 2002;McCord et al 1970).…”

Modelling the internal structure of Ceres: Coupling of accretion with compaction by creep and implications for the water-rock differentiation

“…It orbits the Sun with a semi-major axis of 2.7654 AU. Considered as a protoplanet along with Pallas and Vesta (e.g., Russell et al 2004;McCord et al 2006), Ceres can be considered as one of the few remaining witnesses of the process of planetary accretion.…”

Asteroid-meteorite links: the Vesta conundrum(s)

“…Dawn, the 9th mission in NASA's highly successful Discovery Program, will undertake a detailed study of the geophysics, mineralogy, and geochemistry for two of the largest main belt asteroids (Russell et al, 2004). Dawn is scheduled to be launched in 2006 and will rendezvous with Vesta in 2011 and with Ceres in 2016.…”