Zircon crystals from Western Australia's Jack Hills region were proposed as the oldest evidence of Earth being ready to support life in the Feb. 23, 2014, edition of the journal Nature Geoscience by an international team of researchers led by University of Wisconsin-Madison geoscience Professor John Valley.
The zircons were determined to be 4.4 billion years old. This indicates the Earth’s crust formed about 160 million years after the formation of the universe. The discovery indicates that Earth was capable of retaining water from condensation or from impact from an extraterrestrial source. Two of the necessities for life as it is known on Earth are rock and water.
The scientists used atom-probe tomography and secondary ion mass spectrometry to produce the most exact date for the zircons in the early crust sample that have ever been known. Lead isotope analysis and oxygen isotope analysis confirmed the age of the zircons in the Earth’s oldest known crust.
The research proves that Earth cooled and became habitable much earlier than was previously thought. The probable collision with Mars that formed the Earth’s Moon may have served to accelerate the cooling of the Earth’s crust from a molten state according to the researchers.
Earth was ready for life 4.4 billion years ago.