Bernard Marty, Katherine R. Bermingham, Larry R. Nittler, Sean N. Raymond
Comets III, pp. 681–729.
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Abstract :
Understanding the origin of comets requires knowledge of how the solar system formed from a cloud of dust and gas 4.567 G.y. ago. Here, a review is presented of how the remnants of this formation process — meteorites and to a lesser extent comets — shed light on solar system evolution. The planets formed by a process of collisional agglomeration during the
first hundred million years of solar system history. The vast majority of the original population of planetary building blocks (~100-km-scale planetesimals) was either incorporated into the planets or removed from the system, via dynamical ejection or through a collision with the Sun. Only a small fraction of the original rocky planetesimals survive to this day in the
form of asteroids (which represent a total of ~0.05% of Earth’s mass) and comets. Meteorites are fragments of asteroids that have fallen to Earth, thereby providing scientists with samples of solar-system-scale processes for laboratory-based analysis. Meteorite datasets complement cometary datasets, which are predominantly obtained via remote observation as there are few
cometary samples currently available for laboratory-based measurements. This chapter discusses how analysis of the mineralogical, elemental, and isotopic characteristics of meteorites provides insight into (1) the origin of matter that formed planets; (2) the pressure, temperature, and chemical conditions that prevailed during planet formation; and (3) a precise chronological framework of planetary accretion. Also examined is the use of stable isotope variations and nucleosynthetic isotope anomalies as constraints on the dynamics of the disk and planet formation, and how these data are integrated into new models of solar system formation. It concludes with a discussion of Earth’s accretion and its source of volatile elements, including water and organic species.