This beautifully blue speck of zircon crystal is dated to around 4.4 billion years old, making it the earliest confirmed piece of the planet’s crust and providing some clues about how life on Earth came to be.
The ancient crystal was found in the sticks of Western Australia at a remote rock outcrop called Jack Hills. In a 2014 study, scientists dated the discovery to 4.39 billion years old, give or take a few million years, making it the oldest geological material ever found on Earth.
Even before this research, zircons were known to be some of the oldest materials on Earth, forming as a mineral within certain magmas as they cool. They’re tough as nails and capable of surviving for billions of years, even when subject to intense heat or pressure. This makes them perfect time capsules from Earth’s early history.
Bear in mind, this particular zircon crystal is absolutely tiny, barely visible to the naked eye. Despite its microscopic size, however, it holds some huge implications.
.jpg "Timescale shows just how early this zircon formed in the history of Earth.")
Timescale shows just how early this zircon formed in the history of Earth. Image credit: Andree Valley
Its date of origin was a mere 160 million years after the formation of our solar system. This means it was created just tens of millions of years after an early proto-Earth collided with a giant Mars-size object, creating our Moon in the process and turning our planet into a glowing red ball of molten rock.
However, this speck of zircon suggested that this fiery hellhole didn’t last for too long. If zircon was around 4.4 billion years ago, then Earth must have cooled and congealed by then, forming a crust. Working within this time frame, the prehistoric zircon serves as evidence that Earth developed liquid water environments around 4.3 billion years ago and possibly life shortly after.
“This confirms our view of how the Earth cooled and became habitable. This may also help us understand how other habitable planets would form,” Professor John Valley, a geochemist at the University of Wisconsin-Madison, said in 2014.
“The Earth was assembled from a lot of heterogeneous material from the solar system,” added Valley. “Our samples formed after the magma oceans cooled and prove that these events were very early.”
