Uranium–lead, extraterrestrial, early solar system

Abstract

The U–Pb system is a powerful and versatile chronometer of the early solar system materials and processes. Pb-isotopic dates show that CAIs formed 4567.2– 4567.4 million years ago, chondrules formed during the following 3–4 million years, and differentiated asteroids formed between 1–2 and 10 million years after CAIs. This age distribution is consistent with an astronomical evidence on the rates of evolution of protoplanetary disks and suggests that, during accretion, our solar system comprised an assembly of hot and cold domains, pristine dust, and partially molten planetesimals that coexisted and interacted for less than 10 million years. Subsequent metamorphic events and cooling of asteroids can be studied by Pb-isotopic dating of silicate and phosphate minerals from the same meteorite. Combining U–Pb with short-lived radionuclide chronometers helps to construct a timescale with higher resolution, tests it for internal consistency, and gives us hints to the environment of the solar system formation.