Scientists extract air 1.4 billion years old from a rock salt “time capsule”

Scientists have managed to extract 1.4 billion-year-old air trapped in rock salt crystals, obtaining a rare sample of Earth’s ancient atmosphere. The air revealed levels of oxygen and carbon dioxide higher than experts predicted, suggesting a milder and more moderate climate.

There are more than billion yearsin a shallow basin of what is now northern Ontario, a subtropical lake, similar to today’s Death Valley, evaporated under the gentle action of the sun, leaving behind halite crystalsalso known as sal-gemaa mixture of sodium chloride, accompanied by potassium chloride and magnesium chloride, which occurs in deposits on the Earth’s surface.

The world was then very different than we know today. Bacteria dominated life on Earth. Red algae had just appeared on the evolutionary landscape. Complex multicellular organisms, such as animals and plants, would only appear about 800 million years later.

As the water evaporated, some of it became trapped in tiny pockets inside the crystals, effectively freezing in time. These fluid inclusions contain air bubbles which reveal, in impressive detail, the composition of the early Earth’s atmosphere.

The crystals were then buried by sediment, remaining isolated from the rest of the world for 1.4 billion years, their secrets remained hidden – until now.

In a new study, a team of researchers from Rensselaer Polytechnic Institute (RPI), led by doctoral student Justin Parkunder the guidance of Professor Morgan Schalleranalyzed the composition of gases and liquids trapped in ancient halite crystals from northern Ontario, and managed to backtrack the direct record of Earth’s atmosphere in about 1.4 billion years.

The results were recently published in the journal Proceedings of the National Academy of Sciences.

“It’s an incredible feeling open an air sample that is a billion years old older than dinosaurs”, commented Park, in one from RPI.

Scientists have long known that fluid inclusions in halite crystals can store samples of the primitive atmosphere of Earth. However, obtaining accurate measurements from these samples has been a huge challenge: the inclusions contain bubbles of air and brine, and gases such as oxygen and carbon dioxide behave differently in water than in air.

Correcting these differences to obtain reliable gas readings as they existed in ancient atmospheres, It’s been an arduous task. Park was able to solve the problem, thanks in part to custom equipment developed in Schaller’s lab. Researchers have applied these methods to study the Earth’s atmosphere. Mesoproterozóico.

“The carbon dioxide measurements that Justin obtained had never been done before,” Schaller explained. “We had never been able to look at this era in Earth’s history with such rigor. They are, in fact, samples of ancient air!”.

The results of the study show that the Mesoproterozoic atmosphere contained about 3.7% of the oxygen that currently exists — surprisingly high value, enough to support complex multicellular animal lifealthough it only appeared hundreds of millions of years later.

Carbon dioxide was ten times more abundant than today — enough to offset the so-called “Young and Faint Sun” and create a climate similar to the current one.

It then appears a natural question: if there was enough oxygen to sustain animal life, Why did it take so long to evolve??

Park emphasizes that the sample represents just one instant of the geological scale. “May reflect a brief, transitory event of oxygenation in this long era that geologists jokingly call the ””, he said. It was a period in Earth’s history marked by low levels of oxygen, great atmospheric and geological stability and few evolutionary changes.

“Despite the name, having direct observational data from this period is extremely important because it helps us better understand how complex life came about on the planet and how our atmosphere has evolved to what it is today,” added Park.

Previous indirect estimates of carbon dioxide levels during this period pointed to values ​​too lowincompatible with other observations that show that there were no significant glaciations during the Mesoproterozoic.

The direct measurements now obtained, combined with temperature values ​​estimated from the salt itself, suggest that the climate of this period was milder than previously thought — similar to the current one.

Schaller also highlights that the red algae they emerged precisely at this time in Earth’s history and continue, even today, to be an important source of oxygen on a global level. The relatively high oxygen levels may be a direct consequence of increased abundance and complexity of these algae.

“It’s possible that what we captured is actually an exciting moment right in the middle of the so-called ‘dull billion’”, he concluded.