Geological History of Asteroid 4 Vesta: The “Smallest Terrestrial Planet”

The asteroid 4 Vesta is the only known differentiated asteroid with an intact internal structure, probably consisting of a metal core, an ultramafic mantle, and a basaltic crust. Considerable evidence suggests that the HED meteorites are impact ejecta from Vesta, and detailed studies of these meteorites in terrestrial laboratories, combined with ever more sophisticated remote sensing studies of the asteroid, have resulted in a good understanding of the geological evolution of this fascinating object. Extensive mineralogical, petrological, geochemical, isotopic, and chronological data suggest that heating, melting, and formation of a metal core, a mantle, and a basaltic crust took place in the first few million years of solar system history. It is likely that many more Vesta-like asteroids formed at the dawn of the solar system but were destroyed by impact, with the iron meteorites being remnants of their cores. Such differentiated objects may have played an important role in the accretion and formation of the terrestrial planets, and it is therefore highly desirable to explore by spacecraft this world that can be viewed as the smallest of the terrestrial planets.