Solar system chronology

These isotopes are sometimes used as tracers of natural terrestrial processes and cycles. Long-lived isotopes, such as Rb and Sm are used for precise dating of geological samples. When the solar system formed it also contained several short-lived isotopes that have since decayed and are now extinct in natural systems. These include Al, Fe, Pu, Pd, and Al with a half-life of less than a million years is particularly important because it is a potentially powerful heat source for planetary bodies and because its existence in the early solar system places tight constraints on the early solar system chronology. 

In this chapter we compare the evolution of protoplanetary disks to that of the proto-solar nebula. We start by summarizing the observational constraints on the lifetime of protoplanetary disks and discuss four major disk-dispersal mechanisms. Then, we seek constraints on the clearing of gas and dust in the proto-solar nebula from the properties of meteorites, asteroids, and planets. Finally, we try to anchor the evolution of protoplanetary disks to the Solar System chronology and discuss what observations and experiments are needed to understand how common is the history of the Solar System. 

Figure 9.5 Summary of the timescales for the formation of chondrules, asteroids, and planets in the Solar System compared to the lifetime of disks around young stars. The Solar System chronology is based on the dating of the CAIs, which, we assume, formed within the first Myr of disk evolution. The inner-disk frequency is from infrared excess measurements of stars in different stellar groups (see Section 9.1.1). The timescale for the outer-disk dispersal is discussed in Sections 9.1.1 and 9.1.2. The Solar System chronology is summarized in Section 9.3. For the formation timescales of giant planets, we used those in Desch (2007) with the assumption that outer-disk planetesimals formed 2 Myr after CAIs.

Table 9.1 Summary of the disk lifetimes and comparison with the formation timescale of chondrules, asteroids, and planets in the Solar System. Note that the Solar System chronology is based on the dating of the CAIs, the oldest known solids in the Solar System.

There are two types of refractory inclusions calcium- and aluminum-rich inclusions (this section) and amoeboid olivine aggregates (Section 1.07.5.3). Since the mineralogy, chemistry and isotope chemistry of refractory inclusions were reviewed by MacPherson et al. (1988), many new analyses have been made of CAIs in CV, CM, CO, CR, CH, CB, ordinary and enstatite chondrites that provide important constraints on physicochemical conditions, time, and place of CAI formation. CAIs are addressed in detail in Chapter 1.08, the role of condensation and evaporation in their formation in Chapter 1.15, and their clues to early solar system chronology in Chapter 1.16. 

Gilmour JD, Whitby JA, Turner G, Bridges JC, Hutchison R (2000) The iodine-xenon system in clasts and chondrules from ordinary chondrites implications for early Solar System chronology. Meteoritic Planet Sci 35 445-455... 

Yin, Q.Z., Jacobsen, S.B., Blichert-Toft, J., Telouk, P., and AlbarMe, F. (2001) Nb-Zr and HT-W isotope systematics applications to early solar system chronology and planetary differentiation, 32nd Lunar and Planetary Science Conference, 12-16 March 2001, Houston, TX, Abstract 2128. 

D., Leya, I., and Mezger, K. (2010) Non-nucleosynthetic heterogeneity in non-radiogenic stable Hf isotopes implications for early solar system chronology. Earth Planet. Sci. Lett., 295, 1-11. 

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