Oldest rocks in Australia unlock secrets of the atmosphere

June 27, 2016 by Aaron Fernandes, Sciencenetwork Wa, Science Network WA
Oldest rocks in Australia unlock secrets of the atmosphere
The micrometeorites we extracted travelled through the atmosphere about 2.7 billion years ago ago. Credit: iStock

Research into micro-meteorites, meteorites smaller than 2 millimeters, found in Western Australia have shed new light on the make-up of the ancient Earth's atmosphere.

The Pilbara region in the north of Western Australia has the oldest rocks in Australia, and some of the oldest in the world. Most have barely changed since they were deposited as sediments billions of years ago which allows researchers to unlock secrets of the atmosphere.

"The micrometeorites we extracted travelled through the atmosphere about 2.7 billion years ago. That period is called the Archean Era," says Monash University's Dr Andrew Tomkins.

"Imagine an impact between two asteroids in space. Most meteorites have metal particles in them, so when two asteroids collide, lots of fragments come off, and you end up with cosmic dust.

When that dust enters the Earth's atmosphere, researchers estimate it is moving at more than 12 kilometers a second. Because it's moving so fast, the fragments can also reach temperatures of more than 1500 degrees.

"As the micrometeorite is traveling at great speed and high temperature, it comes into contact with the Earth's atmosphere which causes it to slow down and cool off." Prof Tomkins says.

"When these micrometeorites land on Earth, that information is stored. If that micrometeorite lands in a lake, it can get buried in sediments and becomes preserved in rock".

Dr Tomkins says his research investigated the interactions between the micrometeorites and the to reveal how the ancient atmosphere differed from today.

"We targeted a type of sedimentary rock, called limestone, because it is easily dissolved to reveal the micrometeorites," he says.

"Those particular micrometeorites had been bits of metal floating around in space."

As the micrometeorites reacted with the oxygen and iron in the atmosphere, it turned from iron mostly, to iron-oxide.

"That told us that there had to be a certain level of oxygen available to do that," Prof Tompkin says.

Imperial College researcher Dr Matthew Genge performed calculations that showed oxygen concentrations in the upper atmosphere would need to be close to modern day levels to explain the observations.

"What we had done was found a way to show that there was more oxygen than previously expected, and less carbon monoxide," Dr Tomkins says.

"The findings show the upper atmosphere was oxygen-rich, whilst still allowing the possibility that the lower atmosphere was oxygen-poor. It is basically the first time anybody has been able to figure out a way to look at the chemistry of the upper atmosphere billions of years ago."

Explore further: Cosmic dust reveals Earth's ancient atmosphere

Related Stories

Cosmic dust reveals Earth's ancient atmosphere

May 11, 2016

Using the oldest fossil micrometeorites - space dust - ever found, Monash University-led research has made a surprising discovery about the chemistry of Earth's atmosphere 2.7 billion years ago.

Rust under pressure could explain deep Earth anomalies

June 8, 2016

Using laboratory techniques to mimic the conditions found deep inside the Earth, a team of Carnegie scientists led by Ho-Kwang "Dave" Mao has identified a form of iron oxide that they believe could explain seismic and geothermal ...

Recommended for you

Researchers make coldest quantum gas of molecules

February 21, 2019

JILA researchers have made a long-lived, record-cold gas of molecules that follow the wave patterns of quantum mechanics instead of the strictly particle nature of ordinary classical physics. The creation of this gas boosts ...

Sculpting stable structures in pure liquids

February 21, 2019

Oscillating flow and light pulses can be used to create reconfigurable architecture in liquid crystals. Materials scientists can carefully engineer concerted microfluidic flows and localized optothermal fields to achieve ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.