The Dawn Mission to Minor Planets 4 Vesta and 1 Ceres
DAWN is the first mission to orbit a main belt asteroid and the first scientific mission to use ion propulsion. Major objectives of this mission include mapping of the surfaces of 4 Vesta and 1 Ceres, determining its topography from stereo mea
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The Origin and Evolution of the Asteroid Belt—Implications for Vesta and Ceres David P. O’Brien · Mark V. Sykes
Received: 11 February 2011 / Accepted: 28 June 2011 / Published online: 5 August 2011 © Springer Science+Business Media B.V. 2011
Abstract Vesta and Ceres are the largest members of the asteroid belt, surviving from the earliest phases of Solar System history. They formed at a time when the asteroid belt was much more massive than it is today and were witness to its dramatic evolution, where planetary embryos were formed and lost, where the collisional environment shifted from accretional to destructive, and where the current size distribution of asteroids was sculpted by mutual collisions and most of the asteroids originally present were lost by dynamical processes. Since these early times, the environment of the asteroid belt has become relatively quiescent, though over the long history of the Solar System the surfaces of Vesta and Ceres continue to record and be influenced by impacts, most notably the south polar cratering event on Vesta. As a consequence of such impacts, Vesta has contributed a significant family of asteroids to the main belt, which is the likely source of the HED meteorites on Earth. No similar contribution to the main belt (or meteorites) is evident for Ceres. Through studies of craters, the surfaces of these asteroids will offer an opportunity for Dawn to probe the modern population of small asteroids in a size regime not directly observable from Earth. Keywords Asteroids · Asteroid dynamics · Asteroid collisional evolution · Asteroid Vesta · Asteroid Ceres · Asteroid families · Planet formation · Impacts
1 Background Ceres and Vesta are the most massive objects in the main asteroid belt between Mars and Jupiter, and are surviving representatives of a much larger population of protoplanets and planetary embryos that existed very early in the Solar System. Compositionally, Vesta and Ceres are distinct in that they seem to have formed on opposite sides of the snow line of the time. Ceres accreted ices and primitive carbonaceous material, while Vesta accreted higher-temperature rocky material. Both underwent significant thermal evolution, likely due to the decay of 26 Al. Vesta largely melted and differentiated, forming a metal-rich core D.P. O’Brien () · M.V. Sykes Planetary Science Institute, 1700 E. Ft. Lowell, Suite 106, Tucson, AZ, USA e-mail: [email protected]
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D.P. O’Brien, M.V. Sykes
Fig. 1 The location of Vesta (blue) and Ceres (red) in the asteroid belt. Solid points are their proper orbital elements (Knezevic and Milani 2003), and gray points are the proper orbital elements of 100,000 numbered asteroids. Green points are proper elements of all numbered members of the Vesta family identified by Nesvorny (2010). Asteroids above the blue and red lines in the left plot can cross the orbits of Vesta and Ceres, respectively. The main mean-motion and secular resonances are also shown. Asteroid families, arising largely from the disruption or crater
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