Radioactive dating of meteorites
material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.
Following the development of radiometric age-dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.
Some evidence is also presented to show that radiometric results that are in agreement with the accepted geological time scale are selectively published in preference to those results that are not in agreement.
Many radioisotope dating studies in the last six decades have used the K-Ar, Ar-Ar, Rb-Sr, Sm-Nd, U-Th-Pb, Lu-Hf, Re-Os, Mn-Cr, Hf-W, Al-Mg, I-Xe, and Pu-Xe methods to yield an abundance of isochron and model ages for these achondrites from whole-rock samples, and mineral and other fractions.
Radioactive dating shows them to be about 4.6 billion years old, meaning that they have remained essentially unchanged since they first accreted in the solar nebula. They are pieces of rock that accreted in the solar nebula and orbited the Sun for billions of years before finally falling to Earth.
The individual flakes may represent the tiny particles that first condensed from the gas of the solar nebula.
Since 1955 the estimate for the age of the Earth has been based on the assumption that certain meteorite lead isotope ratios are equivalent to the primordial lead isotope ratios on Earth.
In 1972 this assumption was shown to be highly questionable.
Such age data for 10 of these achondrites were tabulated and plotted on frequency versus age histogram diagrams.