4.4-Billion-Year-Old Crystal Is Earth’s Oldest Fragment

By Carl Engelking | February 24, 2014 1:37 pm
A 4.4 billion-year-old zircon crystal is providing new insight into how the early Earth cooled from a ball of magma and formed continents just 160 million years after the formation of our solar system, much earlier than previously believed. The zircon, pictured here, is from the Jack Hills region of Australia and is now confirmed to be the oldest bit of the Earth's crust. Credit: Image courtesy of John W. Valley

The zircon pictured here is now confirmed to be the oldest bit of the Earth’s crust. Image courtesy of John W. Valley/University of Wisconsin-Madison.

We all know Earth is a pretty cool place, but it’s been cool longer than previously thought. Using two dating techniques, scientists have confirmed that a tiny zircon, a mineral belonging to the group of neosilicates, from Western Australia’s Jack Hills region is indeed the oldest fragment of Earth’s crust, dating back 4.4 billion years.

The findings, from a team of researchers led by University of Wisconsin-Madison geoscience Professor John Valley, strengthen Valley’s theory that the infant planet was cool enough to support oceans and perhaps microbial life just 160 million years after the formation of the solar system.

Dating the Crystals

Thirteen years ago, Valley’s team dated the Jack Hills zircon crystal by analyzing how much of the element uranium decayed into lead within the crystal’s structure. Valley’s team calculated that the zircon crystal — about the width of two human hairs— was 4.4 billion years old.

However, other researchers thought the team’s dating technique could be flawed. They hypothesized that lead atoms moved around inside the crystal, which could lead to an older age measurement.

The latest findings show the team correctly dated the ancient crystal.

To confirm they had the date right all along, Valley’s team used a technique called atom-probe tomography, which deduces the lateral location of atoms. Using this technique, they identified individual lead atoms that were clustered together in the crystal, determined their mass, and confirmed the zircon was 4.4 billion years old. They published their findings this week in the journal Nature Geoscience.

“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 in a news release from UW-Madison. “This allows us to read a new page of the thermal history recorded by these tiny zircon time capsules.”

Our Cool Planet

About 4.5 billion years ago, a Mars-sized object smacked into early Earth, turning our planet into an inhospitable, molten red sphere and providing the raw material for our moon. Valley’s zircon crystals formed just tens of millions of years after the collision, which means Earth’s crust formed during the first geologic eon of the planet, making it possible for life to take root earlier than previously thought.

“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,” Valley told the Chicago Tribune.

The zircon crystal will help scientists close the gap on the part of Earth’s earliest history that is not widely preserved. It could also help researchers understand how other habitable planets formed.

A timeline of the history of our planet places the formation of the Jack Hills zircon and a "cool early Earth" at 4.4 billion years. Credit: Timline courtesy of Andree Valley/University of Wisconsin-Madison

A timeline of the history of our planet places the formation of the Jack Hills zircon and a “cool early Earth” at 4.4 billion years.
Timline courtesy of Andree Valley/University of Wisconsin-Madison.

CATEGORIZED UNDER: Environment, top posts
MORE ABOUT: earth science
  • http://blogs.discovermagazine.com Brian Jeffs

    Typo you wrote 4.4 millions years old in the story.

    • Anonymous MFPatch Commenter

      Carl is a former Patch editor. He isn’t quite used to this whole being factually correct thing yet. I am sure with time he catch on.

  • Anonymous MFPatch Commenter

    Is it Billion or Million?

  • beanfeast

    Is it just me being very easily impressed, but doesn’t anyone else find the detection technique truly wonderful. I’ve read several articles about this story today and none of them explain what they are actually doing – and it only gets half a short paragraph here.

    If I understand it correctly they are taking a very small sample, something like a few tens or hundreds of thousands of cubic nanometres, and ablating it atom by atom and then counting, identifying and recording the original position of each atom.

    Assuming my understanding is correct then that is simply mind blowing. If it isn’t, can someone please correct me?

  • m12345

    at the moment then the science is for life starting and evolving on earth.
    If we found evidence of life that early, it would come from else where I would say.

    • Ferdinand Marcos 2.0

      I would tend to agree. That doesn’t seem like enough time for anything to get started.

      • ikonografer

        just rank speculation, but given the recent findings for rather large genetic mutations in short periods of time, isn’t that still enough time? idk

        • Ferdinand Marcos 2.0

          I don’t imagine anyone could ever be sure of course, but although what you say is true, I don’t think we should consider genetic mutation the same as random amino acids coming together and organizing themselves into proteins and et cetera.

  • Anonymous MFPatch Commenter

    This is pretty amazing.


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