Professor of geoscience, John Valley of the University of Wisconsin, and others, have used atom-probe tomography for the first time to determine the age of a zircon crystal from the Jack Hills region of Western Australia, dating it to 4.4 billion years ago and so making it the oldest object ever identified on Earth. This indicates that the crystal formed within 160 million years of the formation of the Earth.
The crystal measures 200 by 400 microns, about twice the diameter of a human hair.
“One of the things that we’re really interested in is: when did the Earth first become habitable for life? When did it cool off enough that life might have emerged?” Professor Valley said.
The discovery that the zircon crystal, and thereby the formation of the crust, dates from 4.4 billion years ago suggests that the planet was perhaps capable of sustaining microbial life 4.3 billion years ago, Valley said.
“We have no evidence that life existed then. We have no evidence that it didn’t. But there is no reason why life could not have existed on Earth 4.3 billion years ago,” he added.
The oldest fossil records of life are stromatolites produced by an archaic form of bacteria from about 3.4 billion years ago.
In the following video, Professor Valley talks about the work:
For the original report: http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2075.html