The oldest piece of the Earth's crust was discovered in Western Australia and has been confirmed to be 4.4 billion years old.
According to BBC News, scientists dated the zircon, a rough piece of an old rock in new material, by measuring its uranium and lead atoms. The researchers published their study in the journal Nature Geoscience.
Lead decays into uranium very slowly over a long period of time and the process can effectively be used as a timing clock.
"This confirms our view of how the Earth cooled and became habitable," study lead author John Valley, a geochemist from the University of Wisconsin-Madison, said in a press release. "This may also help us understand how other habitable planets would form."
The sample places the formation of Earth's crust just after its formation 4.6 billion years ago, much sooner than previously believed. Many experts believed the Earth solidified from a giant ball of magma and the new discovery indicates our planet was able to host life soon after forming.
The researchers believe the Earth would have been habitable because the climate would have been cool enough for large bodies of water and a hydrosphere.
"The zircon formed 4.4 billion years ago, and at 3.4 billion years, all the lead that existed at that time was concentrated in these hotspots," Valley said. "This allows us to read a new page of the thermal history recorded by these tiny zircon time capsules."
The researchers conducted their study with a new technique called atom-probe tomography and they also had to count lead atoms individually. The team correctly hypothesized that the lead atoms would be clumped together in the zircon sample, rather than being randomly distributed.
"We've demonstrated this zircon is a closed geochemical system, and we've never been able to do that before," Valley told LiveScience. "There's no question that many zircons do suffer radiation damage, but I think relative to these zircons, this should settle it once and for all."
