BOB HIRSHON (host):
Relics from Earth’s birth. I’m Bob Hirshon and this is Science Update.
Scientists have discovered material in rock deposits that’s nearly unchanged since the formation of our planet, four-and-a-half billion years ago. In the journal Science, University of Quebec geochemist Hanika Rizo says that their mere existence is re-writing the book on Earth’s distant past.
HANIKA RIZO (University of Quebec at Montreal, formerly at the Carnegie Institution for Science):
It is difficult to understand knowing that very early we had this giant impact that formed the moon, and this giant impact we thought for a very long time should have erased everything that was formed before in the Earth.
Now they realize that that moon-forming collision must have been with a much smaller object. The chemical composition of the rock also reveals evidence that the early Earth was rocked by between five and fifteen other collisions that helped shape the core we see today. I’m Bob Hirshon, for AAAS, the science society.