Absolute radiometric dating requires a measurable fraction of parent nucleus to remain in the sample rock. For rocks dating back to the beginning of the solar system this requires extremely long lived parent isotopes, and thus the measurement of the different rocks exact ages becomes in-precise. To be able to distinguish the relative ages of rocks from such old material and get a better time resolution short-lived isotopes that are no longer present in the rock can be used. [26]
At the beginning of the solar system there were several relatively short-lived radionuclides like 26Al, 60Fe, 53Mn, and 129I present within the solar nebula. These radionuclides—possibly produced by the explosion of a supernova—are extinct today but their decay products can be detected in very old material such as meteorites. Measuring the decay products of extinct radionuclides with a mass spectrometer and using isochronplots it is possible to determine relative ages between different events in the early history of the solar system. Dating methods based on extinct radionuclides can also be calibrated with the U-Pb method to give absolute ages. Thus both the approximate age and a high time resolution can be obtained. Generally a shorter half life leads to a higher time resolution at the expense of timescale.
