Crystal clear: How one tiny grain of zircon can tell us so much about our planet

The discovery in Australia of a tiny grain of zircon dating back to 4.374 billion years ago tells us much about the planet’s formative years

Science Editor

A tiny grain of crystal barely visible to the naked eye has confirmed that the Earth is a very ancient place indeed.

Scientists estimate that the crystal of zircon is 4.374 billion years old – give or take six million years – which lies very near to the date when the planet itself formed during the birth of the solar system about 180 million years prior to this.

The zircon grain came from the Jack Hills mountain range of Western Australia and now represents the oldest known piece of terrestrial rock on the planet – though some fallen meteorites and samples of lunar rock brought back to Earth may well be older. Whichever way you look at it, the Earth seems to be a very old place indeed.

Trying to gauge the age of the Earth has a long tradition. James Ussher, the Anglican Archbishop of Armagh and Primate of All Ireland, concluded in 1650 that the moment of creation occurred at nightfall preceding Sunday 23 October 4004BC. Although somewhat laughable by modern scientific standards, it was a remarkable piece of scholarship, weaving as he did the events and genealogies of the Bible with what was known about Greek and Roman history.

Archbishop Ussher concluded that the Earth was created 4,000 years before the birth of Christ and would be destroyed 2,000 years after his death. He was in good company in terms of his dates, by the way. Johannes Kepler, the great German mathematician and astronomer, and Isaac Newton, England’s father of physics, had both calculated that the Earth was created about 4,000 years before Christ.

As geological knowledge gradually replaced Biblical mythology, scholars began to realise that the Earth was far older than anyone had realised. The great geologists of the 19th century produced convincing evidence that some rocks were hundreds of millions of years old, which conveniently gave the time needed to explain the evolution of life and the origin of species by Charles Darwin’s mechanism of natural selection.

We now know that the Earth is far older than even these Victorian gentlemen had imagined. The crystal of zircon is like an ancient geological clock that began to tick some 4.4 billion years ago when the Earth’s first crust began to form above a hot ocean of molten magma. The dating work on the crystal, which was carried out by a team led by John Valley of the University of Wisconsin-Madison, shows that the Earth’s crust began to form relatively soon after the planet itself came into existence, which would extend the age of the origin of life.

Scientists believe the Earth was created about 4.56 billion years ago. This was followed by the violent Hadean eon, when the planet was bombarded repeatedly with asteroids and comets, including the massive planet-sized object that led to the creation of the Moon. It was a few million years after this moon-birth moment that the zircon from the Jack Hills crystallised into a miniature time capsule.

The dating method used to determine its age so precisely is based on the steady and predicable radioactive decay of uranium isotopes to lead. The decay acts like the tick-tock of a geological clock. Knowing what exists now within the crystal lattice allows scientists to estimate the time when the clock started “ticking”. Its timekeeping accuracy is critical because a difference in age of 100 million or 200 million years can make all the difference to knowing what was going on during this earliest phase of the planet’s long history.

The single most important implication of the finding is that the Earth began to cool far earlier than previously thought. It means there was a cool-enough crusty landscape for liquid water to form – perhaps helpfully delivered by icy comets – and so for life itself to begin.

Arts and Entertainment
TVShow's twee, safe facade smashed by ice cream melting scandal
Arts and Entertainment
tv
Arts and Entertainment
Lisa Kudrow, Courtney Cox and Jennifer Anniston reunite for a mini Friends sketch on Jimmy Kimmel Live
tv
Life and Style
tech
PROMOTED VIDEO
News
ebooksAn evocation of the conflict through the eyes of those who lived through it
News
Actor, model and now record breaker: Jiff the Pomeranian
Video
News
REX/Eye Candy
science
Sport
Alexis Sanchez celebrates after scoring his first goal for Arsenal in the Champions League qualifier against Besiktas
sportChilean's first goal for the club secures place in draw for Champions League group stages
News
i100
News
Down time: an employee of Google uses the slide to get to the canteen
scienceBosses are inventing surprising ways of making us work harder
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Teacher

£130 - £131 per day: Randstad Education Chelmsford: Ks1 teacher required for m...

Project Manager (infrastructure, upgrades, rollouts)

£38000 - £45000 Per Annum + excellent benefits package: Clearwater People Solu...

MI Analyst and SQL Developer (SQL, SSAS, SSRS)

£28000 - £32500 Per Annum + 28 days holiday, pension, discounts and more: Clea...

Creative Content Executive (writer, social media, website)

£30000 - £35000 Per Annum + 25 days holiday and bonus: Clearwater People Solut...

Day In a Page

Israel-Gaza conflict: No victory for Israel despite weeks of death and devastation

Robert Fisk: No victory for Israel despite weeks of devastation

Palestinians have won: they are still in Gaza, and Hamas is still there
Mary Beard writes character reference for Twitter troll who called her a 'slut'

Unlikely friends: Mary Beard and the troll who called her a ‘filthy old slut’

The Cambridge University classicist even wrote the student a character reference
America’s new apartheid: Prosperous white districts are choosing to break away from black cities and go it alone

America’s new apartheid

Prosperous white districts are choosing to break away from black cities and go it alone
Amazon is buying Twitch for £600m - but why do people want to watch others playing Xbox?

What is the appeal of Twitch?

Amazon is buying the video-game-themed online streaming site for £600m - but why do people want to watch others playing Xbox?
Tip-tapping typewriters, ripe pongs and slides in the office: Bosses are inventing surprising ways of making us work harder

How bosses are making us work harder

As it is revealed that one newspaper office pumps out the sound of typewriters to increase productivity, Gillian Orr explores the other devices designed to motivate staff
Manufacturers are struggling to keep up with the resurgence in vinyl records

Hard pressed: Resurgence in vinyl records

As the resurgence in vinyl records continues, manufacturers and their outdated machinery are struggling to keep up with the demand
Tony Jordan: 'I turned down the chance to research Charles Dickens for a TV series nine times ... then I found a kindred spirit'

A tale of two writers

Offered the chance to research Charles Dickens for a TV series, Tony Jordan turned it down. Nine times. The man behind EastEnders and Life on Mars didn’t feel right for the job. Finally, he gave in - and found an unexpected kindred spirit
Could a later start to the school day be the most useful educational reform of all?

Should pupils get a lie in?

Doctors want a later start to the school day so that pupils can sleep later. Not because teenagers are lazy, explains Simon Usborne - it's all down to their circadian rhythms
Prepare for Jewish jokes – as Jewish comedians get their own festival

Prepare for Jewish jokes...

... as Jewish comedians get their own festival
SJ Watson: 'I still can't quite believe that Before I Go to Sleep started in my head'

A dream come true for SJ Watson

Watson was working part time in the NHS when his debut novel, Before I Go to Sleep, became a bestseller. Now it's a Hollywood movie, too. Here he recalls the whirlwind journey from children’s ward to A-list film set
10 best cycling bags for commuters

10 best cycling bags for commuters

Gear up for next week’s National Cycle to Work day with one of these practical backpacks and messenger bags
Paul Scholes: Three at the back isn’t working yet but given time I’m hopeful Louis van Gaal can rebuild Manchester United

Paul Scholes column

Three at the back isn’t working yet but given time I’m hopeful Louis van Gaal can rebuild Manchester United
Kate Bush, Hammersmith Apollo music review: A preamble, then a coup de théâtre - and suddenly the long wait felt worth it

Kate Bush shows a voice untroubled by time

A preamble, then a coup de théâtre - and suddenly the long wait felt worth it
Robot sheepdog technology could be used to save people from burning buildings

The science of herding is cracked

Mathematical model would allow robots to be programmed to control crowds and save people from burning buildings
Tyrant: Is the world ready for a Middle Eastern 'Dallas'?

This tyrant doesn’t rule

It’s billed as a Middle Eastern ‘Dallas’, so why does Fox’s new drama have a white British star?