The leading explanation for the moon's origin, known as the giant impact hypothesis, suggests that the moon resulted from the collision of two protoplanets, or embryonic worlds.One of those was the young Earth, and the other was a potentially Mars-size object called Theia. [How Earth's Moon Was Made (A Photo Timeline)] "By understanding the moon, we can tell the story of the early bombardment of Earth," study lead author William Bottke, a planetary scientist at the Southwest Research Institute in Boulder, Colorado, told If the sample behaved as a closed system then graphing the difference between the present and initial ratios of Pb should produce a straight line.The distance the point moves along this line is dependent on the U/Pb ratio, whereas the slope of the line depends on the time since Earth's formation. The development of the Geochron was mainly attributed to Clair Cameron Patterson’s application of Pb-Pb dating on meteorites in 1956.Stony meteorites however, exhibited very high Pb ratios, indicating that these samples came from the crust or mantle of the planetesimal.Together, these samples define an isochron, whose slope gives the age of meteorites as 4.55 Byr.
Therefore, troilite found in Canyon Diablo represents the primeval lead isotope composition of the solar system, dating back to 4.55 /- 0.07 Byr.
Therefore, the most precise dating method for these meteorites is the Pb–Pb method, which allows a correction for common Pb.
Pb is relatively low, this isotope has larger measurement errors than the other Pb isotopes, leading to very strong correlation of errors between the measured ratios.
The Pb ratios of three stony and two iron meteorites were measured.
The dating of meteorites would then help Patterson in determining not only the age of these meteorites but also the age of Earth’s formation.