Ancient fossilized space dust teaches us about Earth’s atmosphere

An analysis of ancient space dust found on Earth has revealed that our planet’s ancient atmosphere actually had a lot most oxygen than previously thought, according to a new report in the journal Nature.

The study team based their results on an analysis of “micrometeorites” – or space dust – gathered from ancient limestone in Western Australia.

“Using cutting-edge microscopes we found that most of the micrometeorites had once been particles of metallic iron — common in meteorites — that had been turned into iron oxide minerals in the upper atmosphere, indicating higher concentrations of oxygen than expected,” study author Andrew Tomkins, a geologist from Monash University in Australian, said in a news release. “This was an exciting result because it is the first time anyone has found a way to sample the chemistry of the ancient Earth’s upper atmosphere.”

How does this change our understanding of the Earth’s atmosphere?

The study results challenges the established view that the early Earth had an oxygen-poor atmosphere. The findings instead reveal the ancient Earth’s upper atmosphere held around the same quantity of oxygen as it does today, and that a methane haze layer split this oxygen-rich upper layer from the oxygen-starved atmosphere near the Earth’s surface.

Calculations performed by study author Matthew Genge, a cosmic dust expert from Imperial College London, connected the microscopic observations to the oxygen levels in the ancient atmosphere, and to the oxygen levels in the upper atmosphere today.

“This was a surprise because it has been firmly established that the Earth’s lower atmosphere was very poor in oxygen 2.7 billion years ago; how the upper atmosphere could contain so much oxygen before the appearance of photosynthetic organisms was a real puzzle,” Genge said.

The study team concluded the Earth might have had a stratified atmosphere with minimal vertical mixing, and greater amounts of oxygen in the upper atmosphere generated by the breakdown of carbon dioxide by ultraviolet light.

“A possible explanation for this layered atmosphere might have involved a methane haze layer at middle levels of the atmosphere,” Tomkins said. “The methane in such a layer would absorb UV light, releasing heat and creating a warm zone in the atmosphere that would inhibit vertical mixing.”

“It is incredible to think that by studying fossilized particles of space dust the width of a human hair, we can gain new insights into the chemical makeup of Earth’s upper atmosphere billions of years ago,” he added. “The next stage of our research will be to extract micrometeorites from a series of rocks covering over a billion years of Earth’s history in order to learn more about changes in atmospheric chemistry and structure across geological time.

“We will focus particularly on the great oxidation event, which happened 2.4 billion years ago when there was a sudden jump in oxygen concentration in the lower atmosphere.”

—–

Image credit: Andrew Tomkins

The post Ancient fossilized space dust teaches us about Earth’s atmosphere appeared first on Redorbit.

redOrbit.com
offers Science, Space, Technology, Health news, videos, images and reference information. For the latest science news, space news, technology news, health news visit redOrbit.com frequently. Learn something new every day.”