2006 Annual Science Report
University of Hawaii, Manoa Reporting | JUL 2005 – JUN 2006
Early Accretion of Asteroids and Protoplanets
It is believed that the parent bodies of iron meteorites, i.e., differentiated and subsequently disrupted planetesimals, are formed in the main asteroid belt. Observational evidence, however, does not support this assumption and indicates that differentiated bodies or their fragments were not ever common there. It has recently been noted that the iron-meteorite parent bodies most probably formed in the terrestrial planet region, and fast accretion there allowed small planetesimals to melt early in Solar System history by the decay of short-lived radionuclides (Bottke 2006). The resulting protoplanets caused collisions among the remaining planetesimals and also scattered some of them into the main belt. To investigate this scenario N. Haghighipour has started a new project with Ed Scott and Sasha Krot from NAI/Hawaii, on the accretion and scattering of planetesimals due to the presence of protoplanets in the terrestrial region of our solar system, and in the presence of a growing Jupiter. The model consists of approximately 100 Moon- to Mars-sized objects, and a few hundred smaller bodies, randomly placed from 0.5 to 1.3 AU and 2 to 3 AU from the Sun. The orbits are numerically integrated for 2 million years and for different values of the mass of Jupiter (0.01 to 5 Jupiter-mass). The results have indicated that a few percent of the protoplanets and some of the planetesimals are indeed scattered into the asteroid belt region.
At the second stage of this project, the system is integrated with the orbital parameters as they finish at the end of the 2 million years, and with more asteroids added to the asteroid belt. The goal is to study to what extent the presence of Jupiter will affect the accretion of protoplanets and the scattering of planetesimals to the asteroid belt region.