2009 Annual Science Report
University of Hawaii, Manoa Reporting | JUL 2008 – AUG 2009
Origin of the Parent Bodies of Iron Meteorites and Constraint on Giant Planet Formation
Understanding the origin of the parent bodies of iron meteorites is essential to the theories of planet formation. These objects are formed less then two million years after the formation of the first bodies in the solar system. As a result understanding their formation may reveal clues to the time of the formation of giant planet. We are continuing our project on this topic, and are studying the effects of the growth of giant planets on the dynamics of planetesimals, and their chosmochemical properties.
Being the remnants of the accretion and collision of ~70 planetesimals, iron meteorites provide the best clues to the initial stage of accretion and growth of small bodies in the inner part of the solar system. The parent bodies of these objects were traditionally assumed to have formed in the main asteroid belt. Observational evidence, however, is in disagreement with this assumption and indicates that differentiated bodies are not currently common in that area. It has been suggested that the iron meteorite parent bodies were formed inside 2AU and were scattered into the main belt as a result of interactions with protoplanets. These interactions must have occurred during the growth of giant planets. Haghighipour and his colleagues are continuing their study of the effect of giant planets on the efficiency of the delivery of the parent bodies of iron meteorites to the asteroid belt. The results of their simulations of the collision and scattering of several thousand planetesimals indicate that when the masses of the giant planets became larger than 50M⊕, the perturbations of these objects were the dominant effect. At this stage, the outer protoplanets were strongly affected by the giant bodies and become unstable in a short time. The destabilizing effect of giant planets extends to large distances from these objects within the asteroid belt leaving the inner part of this region less affected by these bodies. Haghighipour’s results also show that in this case, the inner region of the asteroid belt (<2.5 AU) is primarily populated by planetesimals that were out-scattered from the region between 1.5 AU and 2 AU, although some of the innermost planetesimals also contributed (figure 1). Haghighipour is currently continuing his simulations which are expected to portray the perturbative effect of Saturn on the scattering of these objects.