Rock collected by Apollo 17 astronaut in 1972 reveals moon's age

FILE PHOTO: The crescent Earth rises above the lunar horizon in this undated NASA handout photograph taken from the Apollo 17 spacecraft in lunar orbit during the final lunar landing mission in the Apollo program in 1972. REUTERS/NASA/Handout/File Photo

WASHINGTON (Reuters) - During the Apollo 17 mission in 1972 - the last time people walked on the moon - U.S. astronauts Harrison Schmitt and Eugene Cernan collected about 243 pounds (110.4 kg) of soil and rock samples that were returned to Earth for further study.

A half century later, crystals of the mineral zircon inside a coarse-grained igneous rock fragment collected by Schmitt are giving scientists a deeper understanding about the moon's formation and the precise age of Earth's celestial partner.