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Mystery of Earth’s history: Australian crystals are officially oldest material on the planet

A sheep ranch in a remote region of western Australia has yielded one of the most remarkable scientific discoveries of recent times: tiny crystals that are the oldest known materials formed on Earth. The find could offer vital clues to the origin of life on the planet.

The zircon crystals, measuring just twice the diameter of a human hair, were extracted in 2001 from sandstone rock that formed an ancient beach three billion years ago.

A team of researchers used two different methods to date the crystals and found that they date back some 4.4 billion years, just 100 million years after the planet was formed.

This period of Earth’s history is known as the Hadean eon. It was named after Hades, the ancient Greek god of the underworld, because of the hellish conditions that characterised the planet, including a molten surface and frequent meteorite strikes.

But the researchers, writing in the journal Nature Geoscience, said the discovery shows that Earth may have formed a continental crust much earlier than was previously believed and therefore conditions might not have been so harsh.

If this is true, and temperatures at the time were low enough, the planet may have been able to sustain liquid water and possibly even microscopic life much earlier than previously thought.

Geoscience professor John Valley of the University of Wisconsin-Madison, who led the researchers, said: “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.”

Due to plate tectonics and weathering, very little of the Earth’s early surface remains for scientists to study. The vast majority of surface rocks are relatively young in geological terms, less than a few hundred million years old.

For this reason, the tiny zircon crystals found in the Jack Hills region are a vital clue to the mystery of Earth’s early history.

Questions for debate and discussion

  1. What is the connection between these tiny crystals and the history of planet Earth?
  2. Why are scientists so excited about this discovery?
  3. What else do you know about the early history of our planet?
  4. In your opinion, is this kind of research important? Explain your answer.

Relevant resources

Earth’s timeline activity
This memorable on-your-feet activity introduces the vast nature of our planet’s history using toilet roll as a prop.

Planetary Geology
Nasa Education brings you a variety of activities to teach students about the importance of Geology to space exploration.

Darwin’s lost fossils
Watch this video for an insight into the world of early fossil collection, as well as what fossils tell us about the past.

The history of geology and life on earth
In this scavenger hunt, students find out all about how Earth has changed physically over time. 

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