Published online by Cambridge University Press: 05 June 2012
In this chapter, we review what is known about the chronology of the solar system, based on the radioisotope systems described in Chapter 8. We start by discussing the age of materials that formed the solar system. Short-lived radionuclides also provide information about the galactic environment in which the solar system formed. We then consider how the age of the solar system is estimated from its oldest surviving materials – the refractory inclusions in chondrites. We discuss constraints on the accretion of chondritic asteroids and their subsequent metamorphism and alteration. Next, we discuss the chronology of differentiated asteroids, and of the Earth, Moon, and Mars. Finally, we consider the impact histories of the solar system bodies, the timescales for the transport of meteorites from their parent bodies to the Earth, and the residence time of meteorites on the Earth's surface before they disintegrate due to weathering.
Age of the elements and environment in which the Sun formed
The presence of radioactive isotopes in meteorites and planets demonstrates that the atoms that make up our solar system are not infinitely old. On the other hand, the abundance ratios for radioactive species, such as 235U/238U, in the solar system when it formed were much lower than the ratios in which they were produced at the stellar source, as determined from detailed nucleosynthesis models. This indicates that these isotopes were not produced at the time of solar system formation.