Radioisotopes as chronometers

Abstract

Overview So far we have discussed the materials that make up the solar system and the processes that caused those materials to be in their current state. We will now investigate the chronology of the events that led to the current state of the solar system. There are several different approaches to determine the timing of events. The sequence of events can often be established from spatial relationships among objects (e.g. younger things rest on older things). Absolute ages are provided by long-lived radioactive nuclides. Time intervals can be determined using short-lived radionuclides. Production of nuclides through irradiation by cosmic rays can also be used for age determinations. For a complete chronological picture, it is often necessary to use more than one method of age determination. In this chapter, we focus on the basic principles of radiometric dating. We review individual isotopic clocks, the types of materials that each can date, and the measurements that are made to determine the ages of different objects. In Chapter 9, we discuss the chronology of the solar system derived from these clocks. Methods of age determination Placing events in chronological order and attaching an absolute time scale to that order constitute one of the major areas of research in cosmochemistry. There is no single clock that works for everything, so the chronology of the solar system has been built on a wide variety of observations and measurements. The methods of age determination can be divided into two main types.