2. Dating Methods and Corresponding Chronometers in Astrobiology

This chapter concerns the tools with which time or durations are measured in the various disciplines contributing to the chronology of the solar system until the emergence of life. These disciplines and their tools are successively: astronomy (use of the Herzsprung–Russell diagram), geochemistry (radioactive dating), chemistry (no clocks!), and biology (molecular clocks, based on rates of molecular evolution over phylogenetic trees). A final section puts these tools in perspective, showing the impossibility of using a unique clock to describe the evolution of the solar system and of life until today.