NASA Astrobiology Institute (NAI)

1. Dynamical Evolution of Astroid Belt and the Parent Bodies of Iron Meteorites

   Project Investigators: Nader Haghighipour, Ed Scott

   Summary

   This project focuses on the study of the origin and mechanism of the delivery of the parent bodies of iron meteorites to the inner part of the asteroid belt. The goal of the project is to portray a comprehensive picture of the growth and scattering of meteorite parent bodies in the inner part of the solar system by studying the interactions among protoplanets and planetesimals, and the influence of a growing giant planet on the dynamics of these objects.

   Astrobiology Roadmap Objectives:

   • Objective 1.1: Models of formation and evolution of habitable planets

   Project Progress

   Iron meteorites provide the best clues to the nature of the collisions among planetesimals and the initial stage of accretion and growth of small bodies. The parent bodies of these objects were traditionally assumed to have formed and differentiated 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. In an attempt to overcome these difficulties, Bottke et al (2006) suggested that the iron meteorite parent bodies probably formed inside 2 AU and were scattered into the main belt as a result of the collisions and interactions between the protoplanets in that region. The accretion and scattering of planetesimals through interactions with protoplanets must have occurred during the time that the cores of the giant planets were growing. We numerically integrated the orbits of several thousands planetesimals, protoplanets, and a proto-Jupiter to examine the effect of the growth of Jupiter on the accretion and scattering of planetesimals. Our results indicate that
   1) when the mass of the giant planet’s core was smaller than 50M⊕, the perturbation of the giant planet did not play a significant role and the dynamics of planetesimals were mainly governed by their interactions with the planetary embryos.
   2) The range of 50M⊕ to 100M⊕ for the core of the giant planet presents a transitional case. In this case the perturbation of the giant planet were detectable approximately 40% through the simulations.
   3) When the mass of the giant planet was larger than 100M⊕, its perturbation was the dominant effect. Simulations show that in this case, the inner region of the asteroid belt is populated by planetesimals that were back-scattered from the region between 1.5 AU and 2 AU. The forward scattering of outer planetesimals into this region was insignificant.

   
   

   Scattering of planetary embryos. The mass of the giant planet is 50 Earth-mass. In this case, the dominant effect in scattering of protoplanets is the interactions among these objects.

   
   

   Scattering of planetary embryos. The mass of the giant planet is 300 Earth-mass. In this case, the dominant effect in scattering of protoplanets is their interactions with the giant planet.

Publications

Haghighipour, N. & Scott, E.R.D.  (2008).  Meteorite Constraints on the Early Stages of Planetary Growth in the Inner Solar System.  Publications of the Lunar and Planetary Science Conference, 39:1679.