Scientists have used a powerful new technique to prove that some tiny crystals found in Western Australia are indeed the oldest known materials formed on Earth. Back in 2001, scientists reported that one of the zircon crystals was about 4.4 billion years old — so old that not everyone believed it.
"There have been challenges, because nothing in science goes without being questioned. It always has to be proven," says , a geochemist at the University of Wisconsin, Madison.
The crystals formed just tens of millions of years after an early proto-Earth was melted by a violent impact with a Mars-sized object. The crash created the moon and turned our young planet into a red ball of molten rock.