Rock of Ages: Microscopic 4.4 billion-year-old crystal is the oldest-known fragment of Earth
- Microscopic zircon crystal discovered in Western Australia is confirmed to be the oldest known material of any kind formed on Earth
- University of Wisconsin-Madison led study shows early Earth was not as harsh a place as previously thought
- Crystal sheds light on how the planet cooled and became habitable and could help scientists unravel how other life-supporting planets would form
It might looks like just a pretty fragment of crystal, but this blue substance is scientifically significant because it is the oldest piece of Earth, scientists claim.
The tiny piece of zircon crystal was extracted from a rock on a sheep ranch in Western Australia and is a staggering 4.4billion years old.
Despite being microscopic, the crystal is helping scientists unravel how Earth became able to support life.
By analysing the rock, geoscientists have confirmed that the Earth’s crust formed at least 4.4 billion years ago, just 160 million years after the formation of our solar system.
Geoscience Professor John Valley at the University of Wisconsin-Madison has come to the conclusion that Earth was not as harsh a place as scientists previously thought.
The crystal ‘confirms our view of how the Earth cooled and became habitable,’ he said.
Scientists have previously found zircon fragments in sandstone rock, but have not revealed the exact type of rock where they found the ‘new’ sample.
Professor Valley thinks that the study of the zircon crystal has helped portray how the Earth’s crust formed during the first geologic eon of the planet.
‘This may also help us understand how other habitable planets would form,’ he added.
The study, which was published in the journal Nature Geoscience, confirms that microscopic zircon crystals from Western Australia’s Jack Hills region crystallised 4.4 billion years ago.
A few grains of zircon discovered in sandstone rock in Western Australia in the 1990s dated back between 4.2billion and 4.3billion years, so the ‘new’ crystal is at least 100,000 years older.
The team of international scientists led by Professor Valley used lead isotopes to date the Australian zircons and identify them as the oldest bits of the Earth’s crust, as well as the oldest known material of any kind formed on Earth.
Professor Valley said that the study strengthens the theory of ‘a cool early Earth’ where temperatures were low enough for liquid water, oceans and a hydrosphere not long after the planet’s crust congealed from a sea of molten rock.
‘The study reinforces our conclusion that Earth had a hydrosphere before 4.3 billion years ago,’ and possibly life not long after, he said.
The study was conducted using a new technique called atom-probe tomography that along with tried-and-tested ion mass spectrometry, which allowed the scientists to accurately establish the age and thermal history of the zircon by determining the mass of individual atoms of lead in the sample.
Instead of being randomly distributed in the sample as predicted, lead atoms in the zircon were clumped together, like ‘raisins in a pudding,’ Professor Valley explained.
The clusters of lead atoms formed one billion years after crystallization of the zircon, by which time the radioactive decay of uranium had created the lead atoms, which then diffused into clusters during reheating.
‘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,’ Professor Valley said.
‘This allows us to read a new page of the thermal history recorded by these tiny zircon time capsules,’ he added.
The formation, isotope ratio and size of the clumps, which are less than 50 atoms in diameter, can be read like a clock by scientists.
The team of researchers measured oxygen isotope ratios, which give evidence of later cooling of the Earth.
‘The Earth was assembled from a lot of heterogeneous material from the solar system,’ said Professor Valley, who explained that in its infancy, Earth experienced intense bombardment by meteors, including a collision with a Mars-sized object about 4.5 billion years ago.
He said that collision ‘formed our moon, and melted and homogenized the Earth. Our samples formed after the magma oceans cooled and prove that these events were very early.’
WHY ZIRCON ACTS LIKE A CLOCK
Zircon is originally formed by crystallisation of magma and can be found in metamorphic rocks.
The material is durable and resistant to chemical attack so that it is rarely destroyed, according to the American Museum of Natural History.
Zircon can survive many geologic events, which can be recorded in rings of additional zircon that grow around the original crystal like tree rings.
Like a tiny time capsule, the zircon records these events – each one of which may last hundreds of millions of years.
However, the core of the zircon remains unchanged and preserves the chemical characteristics of the rock in which it originally crystallised.
Professor Valley said that early Earth experienced intense bombardment by meteors, including a collision with a Mars-sized object about 4.5 billion years ago. He explained that the collision formed our moon (pictured) and melted the Earth. The zircon crystal formed after the magma oceans cooled and date these events.
More info: http://www.dailymail.co.uk/sciencetech/article-2566588/Rock-Ages-Microscopic-4-4-billion-year-old-crystal-oldest-known-fragment-Earth.html
CeraRoot implants are made of zirconium oxide, also known as zirconia. Zirconium Oxide (Zirconia) is a ceramic material. Keywords: Zirkon Zirkonia Zirkonia zirkonoxid