Fossilized micrometeorites record ancient carbon dioxide content

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Unlike larger brothers, micrometeorites rarely pay attention to museums. However, there are a lot of learning of these extraterrestrial particles, despite the largest of them only millimeters.

Almost 50 tonnes of extraterrestrial materials fall on Earth every day, and most of that cosmic detritus is a minus. Micrometeorites are essentially less than 2 millimeters in diameter, and are commonplace, said Fabian Zahnow, isotopic geochemist Ruhr-Universität Bochum from Germany. “Basically you can find them everywhere.”

Researchers have recently analyzed fossilized micrometeorites that have fallen to Earth millions of years ago. They pulled out the oxygen scents of the inserted atmosphere into particles and showed that carbon dioxide (CO₂) The level of mycen and chalk was not very different from modern values. The results were published in the Communications Earth and the environment.

Extraterrestrial needles rocky mower

The newly fallen micrometeorites can be wiped off from the roofs and dug from the bottom of the lakes.

However, Zahnow and his collaborators chose to turn back: the team analyzed micrometeorites who had fallen to Earth millions of years ago and have since been annoyed. The team sifted over more than a hundred kilograms of sedimentary rocks, mainly in Europe to discover 92 micrometeorites rich in iron. They added eight other iron -dominating micrometeorites from personal collections to make their sample 100 copies.

Metal -rich micrometeorites like these are special, said Zahnow because they act as atmospheric time capsules. When they hurt through the upper atmosphere on the way to the ground, they dissolve and oxidize, which means that the atmospheric oxygen is included in their makeup containing no oxygen.

“When we get them out of the rock record, at best we have our oxygen from the Earth’s atmosphere,” Zahnow said.

The level of ancient carbon dioxide

And that oxygen sees the secrets about the past. It turns out the ratio of atmospheric oxygen isotopes – that is, the relative concentration of three oxygen isotope, ¹⁶Oh, ¹⁷Oh, and ¹⁸O – Correlated with Photosynthesis Quantity and How much CO₂ At the time is. This fact, paired with models of ancient photosynthesis, allowed Zahnow and his colleagues to conclude₂ Concentrations.

The reconstruction of the Earth’s atmosphere, as it was millions of years ago, is important, because atmospheric gas is so fundamentally affected by our planet, said Matt Genge, a scientist of the London Empire College Planets, who has not participated in work. “The History of the atmosphere is the History of Life on Earth.”

However, Zahnow and his collaborators first had to make sure that their micrometeorites were not contaminated with oxygen. The terrestrial water, which has its own unique oxygen isotope ratio, can penetrate the micrometeorites that otherwise reflect the ratio of atmospheric oxygen isotopes. This is a common problem, said Zahnow, taking into account the land everywhere. “There is always water.”

The team found that the presence of manganese in their micrometeorites was worrying that contamination had occurred. “There is virtually no manganese in the extraterrestrial metal,” Zahnow said. “Manganese is actually a spokeswoman for the change.”

Unfortunately, the majority of most researchers were measured by manganese quantities. Eventually, Zahnow and his collaborators thought that only four of their micrometeorites were unclean.

Those micrometeorites that fell to Earth during myceno (9 million years ago) and late chalk (87 million years ago) suggested that CO₂ During those periods, the level was an average of approximately 250-300 parts per million. It is slightly lower than modern levels, which range from about 420 million parts.

The team’s conclusions are in line with the values ​​previously offered, said Genge, but unfortunately, the team numbers are simply not accurate enough to do something significant. “You have a really great uncertainty,” he said.

However, the team’s methods are strong, but said Genge, and the researchers tried hard to appreciate what was actually a weak ancient oxygen whistle. “It’s a bold attempt.”

In the future, it would be valuable to assemble a larger number of undamaged micrometeorites to periods when model reconstruction indicates anomalous high CO₂ Exactly, Zahnow said. “What we really expected was to get undamaged micrometeorites from the periods when the reconstruction says a really high concentration.”

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To confirm the data at such times such as Triassic₂ Exactly would be valuable to understand how life on Earth responded to such a common abundance₂;